A method for efficiently recovering precious metals from waste automobile catalyst

Abstract

This invention provides a method for efficiently recovering precious metals from waste automotive catalysts, belonging to the field of precious metal recycling technology. The method includes: physically crushing and hot ball milling the waste automotive catalyst to obtain activated material; adding a composite activator during the hot ball milling process, the hot ball milling process including pre-activation at 80℃~120℃, carrier pyrolysis at 150℃~200℃, and deep activation at 250℃~300℃; the composite activator includes sodium hydroxide, sodium carbonate, sodium nitrate, and zinc powder; washing the activated material with hot water at 60℃~80℃ until the pH of the washing solution drops to neutral, and separating the solid and liquid to obtain a leaching precursor; adding a leaching solvent to the leaching precursor for oxidative leaching; then adding stannous chloride for complexation leaching; solid-liquid separation, and collecting the leachate; the leaching solvent includes hydrochloric acid, nitric acid, and hydrofluoric acid. This invention achieves efficient leaching and separation of platinum, palladium, and rhodium through the synergistic effect of gradient thermochemical mechanical activation and stepwise leaching.

Description

Technical Field

[0001] This invention belongs to the field of precious metal recycling technology, and specifically relates to a method for efficiently recovering precious metals from waste automotive catalysts. Background Technology

[0002] Automotive catalysts are core components for controlling vehicle exhaust pollution. Their internal carriers (mostly cordierite-supported γ-alumina) are coated with platinum group metals such as platinum, palladium, and rhodium as active components. These precious metals are scarce and expensive, and are crucial for the catalyst's catalytic effect. With the increasing number of vehicles on the road and the expiration of catalyst lifespans, a large amount of waste automotive catalysts are generated annually. Direct disposal not only results in a serious waste of precious metal resources but also causes environmental pollution due to leakage of the carrier and impurities.

[0003] Currently, methods for recovering precious metals from waste automotive catalysts are mainly divided into two categories: pyrometallurgical and hydrometallurgical processes. Pyrometallurgical processes (such as blast furnace smelting and reduction sulfidation smelting) require high-temperature heating, resulting in high energy consumption, large equipment investment, and a tendency to generate secondary pollution. The recovery rate of precious metals is difficult to steadily improve, with some processes achieving only around 90% recovery of platinum group metals. Hydrometallurgical processes (such as aqua regia leaching and hydrochloric acid-oxidant leaching) have lower energy consumption, but suffer from low leaching efficiency, difficulty in separating precious metals, severe impurity interference, and high reagent consumption. Furthermore, some processes require secondary leaching, leading to high labor intensity and high wastewater and waste gas treatment costs, making large-scale industrial application difficult. To address these issues, current precious metal recovery methods are primarily pyrometallurgical-hydrometallurgical combined processes: first, calcination activation at 500℃~900℃, followed by acid leaching. However, these methods still suffer from high energy consumption and low recovery efficiency (mainly rhodium).

[0004] Therefore, developing a method for recovering precious metals from waste automotive catalysts that is simple in process, low in energy consumption, high in recovery rate, environmentally friendly and pollution-free, and can achieve efficient separation and purification of precious metals has become an urgent technical problem to be solved in this field. Summary of the Invention

[0005] In view of this, the present invention provides a method for efficiently recovering precious metals from waste automotive catalysts, aiming to solve at least one of the technical problems in the background art.

[0006] This invention is implemented as follows: A method for efficiently recovering precious metals from waste automotive catalysts, the method comprising the following steps: S1. Waste automotive catalysts undergo physical crushing and hot ball milling to obtain activated material; a composite activator is added during the hot ball milling process, which includes pre-activation at 80℃~120℃, carrier pyrolysis at 150℃~200℃, and deep activation at 250℃~300℃; the composite activator includes sodium hydroxide, sodium carbonate, sodium nitrate, and zinc powder. S2. Wash the activated material with hot water at 60℃~80℃ until the pH of the washing solution drops to neutral, and then separate the solid and liquid to obtain the leaching precursor. S3. Add leaching solvent to the leaching precursor for oxidative leaching; then add stannous chloride for complexation leaching; separate the solid and liquid, and collect the leaching solution as a precious metal enrichment solution; the leaching solvent includes hydrochloric acid, nitric acid and hydrofluoric acid.

[0007] Furthermore, the steps in S1 specifically include: S11. The spent automotive catalyst is coarsely crushed and finely ground to obtain spent catalyst particles with a particle size ≤200 mesh. S12. Place the waste catalyst particles in a ball mill, introduce an inert atmosphere for protection, and ball mill at a low speed of 100r / min to 200r / min for 10min to 30min at a temperature of 80℃ to 120℃ to achieve pre-activation; S13. Increase the temperature to 150℃~200℃, increase the rotation speed to 200r / min~400r / min, add a composite activator accounting for 10%~30% of the mass of the waste automotive catalyst, and ball mill in an inert atmosphere for 10min~30min to achieve carrier pyrolysis. S14. Increase the temperature to 250℃~300℃, increase the rotation speed to 400r / min~600r / min, and maintain an inert atmosphere for ball milling for 30min~60min to achieve deep activation; S15. Keep inert atmosphere and cool to room temperature.

[0008] Furthermore, in S12 to S15, the ball-to-material ratio is 15 to 25:1.

[0009] Furthermore, the composite activator comprises the following components by weight percentage: Sodium hydroxide 40%~60%, Sodium carbonate 20%~40%, Sodium nitrate 5%~15%, Zinc powder 5%~10%.

[0010] Furthermore, the inert atmosphere is at least one of nitrogen or argon.

[0011] Furthermore, in S12 to S14, the heating rate is 2℃ / min to 10℃ / min. Further, the heating rate of S12 is 5℃ / min to 10℃ / min; the heating rate of S13 is 3℃ / min to 7℃ / min; and the heating rate of S14 is 2℃ / min to 5℃ / min. Furthermore, the steps in S3 specifically include: S31. Add the leaching precursor and leaching solvent to the reactor at a solid-liquid ratio of 1:3~6, and oxidize and leach for 30min~60min at a temperature of 90℃~95℃ and a rotation speed of 300r / min~500r / min. S32. Add stannous chloride to the reactor to a final concentration of 8 g / L to 12 g / L, and perform complexation leaching at a temperature of 90℃ to 95℃ and a rotation speed of 300 r / min to 500 r / min for 30 min to 60 min. S33. After leaching, filter while hot and collect the filtrate and filter residue separately. Wash the filter residue with dilute hydrochloric acid and combine the washing liquid with the filtrate to form the leachate.

[0012] Furthermore, in the leaching solvent of S3, the concentration of hydrochloric acid is 4 mol / L to 8 mol / L, the concentration of nitric acid is 1 mol / L to 2 mol / L, and the concentration of hydrofluoric acid is 0.5 mol / L to 1.5 mol / L.

[0013] Compared with the prior art, the present invention has the following beneficial effects: 1. This invention achieves efficient leaching and separation of platinum, palladium, and rhodium through the synergistic combination of gradient thermochemical mechanical activation and stepwise leaching.

[0014] 2. This invention pioneers a gradient thermochemical mechanical activation technology, which couples temperature gradient, chemical gradient and mechanical force gradient to achieve precise activation in three stages: physical stripping, chemical erosion and deep activation.

[0015] 3. This invention utilizes the in-situ reduction effect of composite activators to directly reduce the oxides of Pt, Pd, and Rh into highly active metallic states during ball milling, fundamentally reducing the difficulty of leaching precious metals and reducing the amount of zinc powder used as the main reducing agent.

[0016] 4. This invention adopts a stepwise leaching process of first oxidative leaching and then complexation leaching, which effectively avoids the direct redox reaction between nitric acid and stannous chloride, and improves reagent utilization. At the same time, the stepwise operation eliminates the need for intermediate filtration, simplifies the process, improves leaching efficiency, and reduces leaching time.

[0017] 5. This invention employs a wet process route, which produces no harmful gases throughout the entire process; the activation is carried out under an inert atmosphere, producing no NO. xThe process reduces emissions of waste gases such as SO2; the acid in the leachate can be recycled through a condensation recovery system, reducing waste liquid emissions. The overall process is environmentally friendly and in line with the development direction of green chemical industry. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0019] A method for efficiently recovering precious metals from waste automotive catalysts includes the following steps: S1. Waste automotive catalysts undergo physical crushing and hot ball milling to obtain activated material. A composite activator is added during the hot ball milling process, which includes pre-activation at 80℃~120℃, support pyrolysis at 150℃~200℃, and deep activation at 250℃~300℃. The composite activator includes sodium hydroxide, sodium carbonate, sodium nitrate, and zinc powder. The purpose of this step is to break the physical encapsulation of precious metals on the catalyst support.

[0020] The specific steps in S1 include: S11. The spent automotive catalyst is coarsely crushed and finely ground to obtain spent catalyst particles with a particle size ≤200 mesh.

[0021] S12. Place the waste catalyst particles in a ball mill and introduce an inert atmosphere (nitrogen and / or argon) for protection. Heat the particles from room temperature to 80°C to 120°C at a rate of 5°C / min to 10°C / min (preferably 5°C / min to 7°C / min). Then, ball mill the particles at a low speed of 100r / min to 200r / min for 10 to 30 minutes to achieve pre-activation. Pre-activation is a low-temperature physical exfoliation process, mainly driven by mechanical force. Through the impact and shearing action of ball milling, the catalyst particles are further refined, and the specific surface area is greatly increased. At the same time, the carbon on the surface is physically exfoliated, opening the channels for subsequent chemical erosion.

[0022] S13. Increase the temperature to 150℃~200℃ at a rate of 3℃ / min~7℃ / min, and increase the rotation speed to 200r / min~400r / min. Add a composite activator (40%~60% sodium hydroxide, 20%~40% sodium carbonate, 5%~15% sodium nitrate, and 5%~10% zinc powder) accounting for 10%~30% of the mass of the waste automotive catalyst. Maintain an inert atmosphere and ball mill for 10min~30min to achieve carrier pyrolysis. Carrier pyrolysis is a medium-temperature chemical etching. In this stage, sodium hydroxide (NaOH) reacts with SiO2 in the cordierite carrier to generate soluble Na2SiO3, which destroys the carrier structure from a chemical perspective. Sodium carbonate (Na2CO3) helps to lower the reaction temperature. NaNO3 provides an oxidizing atmosphere to assist in decarburization. Zinc powder begins to play a reducing role. Research in this field has found that adding zinc powder during mechanical activation can effectively improve the leaching rate of precious metals, but the dosage is very high, typically requiring 1 to 2 times the mass of the raw material, waste automotive catalyst. In this step, sodium hydroxide, sodium carbonate, and sodium nitrate are added, which significantly reduces the amount of zinc used while retaining the effect.

[0023] S14. Increase the temperature to 250℃~300℃ at a rate of 2℃ / min~5℃ / min, increase the rotation speed to 400r / min~600r / min, and maintain an inert atmosphere for ball milling for 30min~60min to achieve deep activation. The purpose of deep activation is to promote the complete reaction between the composite activator and the carrier, and thoroughly destroy the residual carrier structure. Zn powder reduces the oxides of Pt, Pd, and Rh in situ to a highly active metallic state.

[0024] S15. Keep inert atmosphere and cool to room temperature.

[0025] The maximum temperature of the hot ball milling process is only 300℃, which is much lower than the pretreatment step of conventional wet process - calcination temperature, and simplifies the post-activation process.

[0026] S2. Wash the activated material with hot water at 60℃~80℃ until the pH of the washing solution drops to neutral, and separate the solid and liquid to obtain the leaching precursor. The activated material contains a large amount of soluble sodium silicate and sodium aluminate. Hot water washing removes the soluble carrier components and reduces the acid consumption in subsequent leaching.

[0027] S3. Add leaching solvent to the leaching precursor at a solid-liquid ratio of 1:3~6 for oxidative leaching; then add stannous chloride for complexation leaching; separate the solid and liquid, and collect the leaching solution as a precious metal enrichment solution; the leaching solvent includes hydrochloric acid, nitric acid and hydrofluoric acid.

[0028] S3 employs a single-stage step-by-step leaching process, specifically including: S31. Add the leaching precursor and leaching solvent to the reactor at a solid-liquid ratio of 1:3~6, and oxidize and leach for 30min~60min at a temperature of 90℃~95℃ and a rotation speed of 300r / min~500r / min. The leaching solvent contains hydrochloric acid at a concentration of 4mol / L~8mol / L, nitric acid at a concentration of 1mol / L~2mol / L, and hydrofluoric acid at a concentration of 0.5mol / L~1.5mol / L. Hydrochloric acid provides chloride ions, which form stable chloride anions with the oxidized noble metal ions. Nitric acid acts as an oxidant, oxidizing noble metals such as platinum, palladium, and rhodium from zero valence to higher valence ions. Hydrofluoric acid acts as a chemical dissolution carrier, corroding and destroying the silicate carriers such as cordierite that encapsulate the noble metals, exposing them. Specifically, it breaks the Si-O bonds and Al-O bonds in the cordierite lattice one by one through a chemical reaction, turning them into soluble fluorosilicates that enter the solution.

[0029] S32. Add stannous chloride to the reactor to a final concentration of 8 g / L~12 g / L, and perform complexation leaching at a temperature of 90℃~95℃ and a rotation speed of 300 r / min~500 r / min for 30 min~60 min; Sn 2+ It forms a stable chlorostannic acid complex anion with the dissolved noble metal ions, preventing the noble metal ions from hydrolyzing and precipitating or re-adsorbing onto the carrier surface. The stepwise addition of chloride effectively avoids direct redox reaction with nitric acid.

[0030] S33. After leaching is completed, filter the solution while it is still hot using a plate and frame filter press. Collect the filtrate and filter residue separately. Wash the filter residue with dilute hydrochloric acid. Combine the washing solution with the filtrate to obtain the precious metal enrichment solution.

[0031] In specific implementations, the process may also include further refining and recovering platinum, palladium, and rhodium, which can employ any refining and recovery process in the art. The specific implementation uses the following steps (S41-S43) for recovery, but is not limited to these; other refining and recovery methods in the art are also applicable.

[0032] S41. Base metal pre-removal: Slowly add saturated Na2S solution to the precious metal enrichment solution, control the pH to 1.5~2.5, stir for 30 min, base metals (Fe, Al, Mg, Ca and Sn introduced during leaching) will form sulfide precipitates, which will be removed by filtration.

[0033] S42. Separation and purification. (1) Selective extraction of palladium: Pd is selectively extracted from the purified solution using diisoamyl sulfide (S201) as the extractant. The concentration of S201 in the organic phase is 10%~20% (v / v), the diluent is kerosene, the ratio (O / A) is 1:1 to 1:3, and the extraction is performed by 3 to 5 stages of countercurrent extraction. The loaded organic phase is back-extracted with thiourea-hydrochloric acid solution to obtain a palladium-containing solution. (2) Selective extraction of platinum: Pt is selectively extracted from the raffinate after palladium extraction using tributyl phosphate (TBP) as the extractant. The concentration of TBP in the organic phase is 20%~30% (v / v), the diluent is kerosene, the ratio (O / A) is 1:1 to 1:2, and the extraction is performed by 3 to 4 stages of countercurrent extraction. The loaded organic phase is back-extracted with dilute hydrochloric acid or water to obtain a platinum-containing solution. (3) Recovery of rhodium: The raffinate after platinum extraction mainly contains Rh. 3+ After using D263 resin to adsorb and recover residual trace amounts of Pt and Pd, ammonium chloride was added to the solution to generate ammonium hexachlororhodium precipitate.

[0034] S43. Refining. (1) Refining of sponge platinum: The platinum-containing solution is dissolved in aqua regia, precipitated with ammonium chloride, calcined and reduced with hydrogen to obtain sponge platinum. (2) Refining of sponge palladium: The palladium-containing solution is dissolved in aqua regia, complexed with ammonia, acidified with hydrochloric acid and reduced with hydrazine hydrate to obtain sponge palladium. (3) Refining of sponge rhodium: The rhodium-containing precipitate is calcined and reduced with hydrogen to obtain sponge rhodium.

[0035] Example 1 A method for efficiently recovering precious metals from waste automotive catalysts includes the following steps: S1. Collect spent automotive catalysts (main precious metal components and contents: platinum (Pt) 350g / t, palladium (Pd) 1607g / t, rhodium (Rh) 164g / t, with cordierite as the carrier). After coarse crushing with a jaw crusher, the spent catalysts are fed into a ball mill for fine grinding and then sieved through a 200-mesh standard sieve to obtain spent catalyst particles. The sieved waste catalyst particles and zirconia grinding balls were loaded into a hot ball mill at a ball-to-material ratio of 20:1. Nitrogen gas was introduced for protection. The temperature was first raised to 100°C at 6°C / min and ball milled at 150 r / min for 25 min. The temperature was then raised to 180°C at 5°C / min, and a composite activator (50% NaOH, 30% Na2CO3, 12% NaNO3, and 8% Zn powder) accounting for 20% of the mass of the waste catalyst particles was added. The mixture was ball milled at 300 r / min for 25 min. The temperature was then raised to 270°C at 4°C / min and ball milled at 500 r / min for 45 min. Under nitrogen protection, the mixture was allowed to cool naturally to room temperature to obtain the activated material.

[0036] S2. The activated material is washed three times with hot water at 70°C until the pH of the washing solution is 7. Solid-liquid separation is performed, and the solid is collected to obtain the leaching precursor.

[0037] S3. Add the leaching precursor to the leaching solvent at a liquid-to-solid ratio of 4:1 (mL:g). The leaching solvent composition is: 6 mol / L hydrochloric acid, 1.5 mol / L nitric acid, and 1.0 mol / L hydrofluoric acid. Oxidize and leach at 90℃~95℃ for 2 hours with a stirring speed of 400 r / min. Add stannous chloride to the reaction system to a concentration of 10 g / L and continue leaching for 1 hour, maintaining the temperature at 90℃~95℃. After leaching, filter while hot using a plate and frame filter press. Wash the filter residue twice with dilute hydrochloric acid. Combine the washing liquid and filtrate to form the leachate, which is the precious metal enrichment solution.

[0038] S4. Slowly add saturated Na2S solution to the precious metal enrichment solution, control pH=2.0, stir for 30 min, and filter to remove sulfide precipitate. Use diisoamyl sulfide (S201) as the extractant, with an S201 concentration of 15% (v / v) in the organic phase, kerosene as the diluent, and an O / A ratio of 1:2, and perform 4-stage countercurrent extraction. Back-extract the loaded organic phase with thiourea-hydrochloric acid solution to obtain a palladium-containing solution. Use tributyl phosphate (TBP) as the extractant, with a TBP concentration of 25% (v / v) in the organic phase, kerosene as the diluent, and an O / A ratio of 1:1.5, and perform 4-stage countercurrent extraction. Back-extract the loaded organic phase with dilute hydrochloric acid to obtain a platinum-containing solution. After platinum extraction, adsorb residual Pt and Pd with D263 resin, add ammonium chloride to generate ammonium hexachlororhodium precipitate. Platinum-containing solution was dissolved in aqua regia, precipitated with ammonium chloride, calcined at 450℃, and reduced with hydrogen at 550℃ to obtain sponge platinum. Palladium-containing solution was dissolved in aqua regia, complexed with ammonia, acidified with hydrochloric acid, and reduced with hydrazine hydrate to obtain sponge palladium. Rhodium-containing precipitate was calcined at 500℃ and reduced with hydrogen at 600℃ to obtain sponge rhodium.

[0039] Example 2 The only difference between this embodiment and the previous embodiment is the condition of the hot ball milling treatment in S1; all other steps and conditions are the same as in embodiment 1.

[0040] Step S1 specifically involves collecting spent automotive catalysts (the main precious metal components and contents are: platinum (Pt) 350 g / t, palladium (Pd) 1607 g / t, rhodium (Rh) 164 g / t, with cordierite as the carrier). The spent catalysts are coarsely crushed using a jaw crusher, then finely ground in a ball mill, and sieved through a 200-mesh standard sieve to obtain spent catalyst particles. The sieved waste catalyst particles and zirconia grinding balls were loaded into a hot ball mill at a ball-to-material ratio of 20:1. Nitrogen gas was introduced for protection. The temperature was first raised to 80°C at 5°C / min and ball milled at 150 r / min for 25 min. The temperature was then raised to 150°C at 3°C / min, and a composite activator (50% NaOH, 30% Na2CO3, 12% NaNO3, and 8% Zn powder) accounting for 30% of the mass of the waste catalyst particles was added. The mixture was ball milled at 300 r / min for 25 min. The temperature was then raised to 250°C at 2°C / min and ball milled at 500 r / min for 45 min. Under nitrogen protection, the mixture was allowed to cool naturally to room temperature to obtain the activated material.

[0041] Example 3 The only difference between this embodiment and the previous embodiment is the condition of the hot ball milling treatment in S1; all other steps and conditions are the same as in embodiment 1.

[0042] Step S1 specifically involves collecting spent automotive catalysts (the main precious metal components and contents are: platinum (Pt) 350 g / t, palladium (Pd) 1607 g / t, rhodium (Rh) 164 g / t, with cordierite as the carrier). The spent catalysts are coarsely crushed using a jaw crusher, then finely ground in a ball mill, and sieved through a 200-mesh standard sieve to obtain spent catalyst particles. The sieved waste catalyst particles and zirconia grinding balls were loaded into a hot ball mill at a ball-to-material ratio of 20:1. Nitrogen gas was introduced for protection. The temperature was first raised to 120°C at 7°C / min and ball milled at 150 r / min for 25 min. The temperature was then raised to 200°C at 7°C / min, and a composite activator (50% NaOH, 30% Na2CO3, 12% NaNO3, and 8% Zn powder) was added at 10% of the mass of the waste catalyst particles. The mixture was ball milled at 300 r / min for 25 min. The temperature was then raised to 300°C at 5°C / min and ball milled at 500 r / min for 45 min. The mixture was kept under nitrogen protection and allowed to cool naturally to room temperature to obtain the activated material.

[0043] Example 4 The only difference between this embodiment and the previous embodiment is the composition of the composite activator in S1; all other steps and conditions are the same as in Example 1.

[0044] In this embodiment, the composite activator in S1 includes 40% NaOH, 40% Na2CO3, 15% NaNO3, and 5% Zn powder.

[0045] Example 5 The only difference between this embodiment and Example 1 is the composition of the composite activator in S1; all other steps and conditions are the same as in Example 1.

[0046] In this embodiment, the composite activator in S1 includes 60% NaOH, 25% Na2CO3, 35% NaNO3, and 10% Zn powder.

[0047] Comparative Example 1 The only difference between this comparative example and Example 1 is the removal of the composite activator in S1; all other steps and conditions are the same as in Example 1.

[0048] Comparative Example 2 The only difference between this comparative example and Example 1 is that NaOH is removed from the composite activator in S1. The composite activator specifically includes 40% Na2CO3, 15% NaNO3, and 45% Zn powder. All other steps and conditions are the same as in Example 1.

[0049] Comparative Example 3 The only difference between this comparative example and Example 1 is that Na2CO3 is removed from the composite activator in S1. The composite activator specifically includes 60% NaOH, 15% NaNO3, and 35% Zn powder. All other steps and conditions are the same as in Example 1.

[0050] Comparative Example 4 The only difference between this comparative example and Example 1 is that NaNO3 is removed from the composite activator in S1. The composite activator specifically includes 50% NaOH, 40% Na2CO3, and 10% Zn powder. All other steps and conditions are the same as in Example 1.

[0051] Comparative Example 5 The only difference between this comparative example and Example 1 is that the composite activator in S1 removes Zn powder, specifically including 52% NaOH, 33% Na2CO3, and 15% NaNO3. All other steps and conditions are the same as in Example 1.

[0052] Comparative Example 6 The only difference between this comparative example and Example 1 is that S1 uses a single temperature (250°C) for hot ball milling; all other steps and conditions are the same as in Example 1.

[0053] The steps of this comparative example of hot ball milling are as follows: the sieved waste catalyst particles and zirconia grinding balls are loaded into a hot ball mill at a ball-to-material ratio of 20:1. Nitrogen gas is introduced for protection. The temperature is first raised to 250℃ at 6℃ / min, and then ball milled at 150r / min for 25min. Then, a composite activator (NaOH 50%, Na2CO3 30%, NaNO3 12%, Zn powder 8%) accounting for 20% of the mass of the waste catalyst particles is added, and ball milled at 300r / min for 25min. Then, ball milled at 500r / min for 45min. Under nitrogen protection, the mixture is allowed to cool naturally to room temperature to obtain the activated material.

[0054] Comparative Example 7 The only difference between this comparative example and Example 1 is that S1 uses a single temperature (room temperature about 30°C) for hot ball milling; all other steps and conditions are the same as in Example 1.

[0055] The steps of the comparative example of hot ball milling are as follows: the sieved waste catalyst particles and zirconia grinding balls are loaded into a hot ball mill at a ball-to-material ratio of 20:1, nitrogen protection is introduced, and the mixture is ball-milled at a speed of 150 r / min for 25 min; then, a composite activator (NaOH 50%, Na2CO3 30%, NaNO3 12%, Zn powder 8%) accounting for 20% of the mass of the waste catalyst particles is added, and the mixture is ball-milled at a speed of 300 r / min for 25 min; then, the mixture is ball-milled at a speed of 500 r / min for 45 min to obtain the activated material.

[0056] Comparative Example 8 The only difference between this comparative example and Example 1 is that stannous chloride and the leaching solvent are added simultaneously in S3; all other steps and conditions are the same as in Example 1.

[0057] Specifically, in Comparative Example S3, the leaching precursor was added to the leaching solvent at a liquid-to-solid ratio of 4:1 (mL:g). The leaching solvent consisted of 6 mol / L hydrochloric acid, 1.5 mol / L nitric acid, and 1.0 mol / L hydrofluoric acid, with stannous chloride added to a concentration of 10 g / L. Oxidative leaching was carried out at 90℃~95℃ for 3 hours, maintaining the temperature at 90℃~95℃. After leaching, the mixture was filtered while still hot using a plate and frame filter press. The filter residue was washed twice with dilute hydrochloric acid, and the washings were combined with the leaching solution to form the precious metal enrichment solution.

[0058] The recovery rates of platinum group metals in Examples 1 to 5 and Comparative Examples 1 and 8 of this invention were calculated, and the results are shown in Table 1. Three parallel experiments were set up for each example, and the data are mean ± standard deviation. The platinum / palladium / rhodium recovery rate was obtained by calculating the ratio of the mass of pure metal in the refined sponge metal to the theoretical mass of the metal in the spent catalyst feedstock. The mass of pure metal was determined by multiplying the total mass of the refined product by its measured purity. The theoretical mass of the metal in the feedstock was determined by ICP-OES analysis after digestion of representative feedstock samples.

[0059] Table 1

[0060] Table 1 shows that the methods in Examples 1 to 5 of this invention achieve efficient recovery of platinum, palladium, and rhodium.

[0061] Compared with Example 1, Comparative Examples 1 to 5 removed the composite activator or any of its components. The results showed that the recovery rates of platinum, palladium and rhodium were significantly reduced, and the standard deviation (SD) was significantly greater than that of Example 1, indicating that the recovery effect was unstable and fluctuated greatly.

[0062] Compared with Example 1, Comparative Examples 6 and 7 were ball-milled at constant temperatures (250°C and 30°C), and the results showed that the recovery rates of platinum, palladium, and rhodium decreased significantly.

[0063] Compared with Example 1, in Comparative Example 8, stannous chloride was added simultaneously with the leaching solvent, and the results showed that the recovery rates of platinum, palladium and rhodium were all significantly reduced.

[0064] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. A method for efficiently recovering precious metals from waste automotive catalysts, characterized in that, The method includes the following steps: S1. Waste automotive catalysts undergo physical crushing and hot ball milling to obtain activated material; a composite activator is added during the hot ball milling process, which includes pre-activation at 80℃~120℃, carrier pyrolysis at 150℃~200℃, and deep activation at 250℃~300℃; the composite activator includes sodium hydroxide, sodium carbonate, sodium nitrate, and zinc powder. S2. Wash the activated material with hot water at 60℃~80℃ until the pH of the washing solution drops to neutral, and then separate the solid and liquid to obtain the leaching precursor. S3. Add leaching solvent to the leaching precursor for oxidative leaching; then add stannous chloride for complexation leaching. Solid-liquid separation is performed, and the leachate is collected as a precious metal enrichment solution; the leaching solvent includes hydrochloric acid, nitric acid, and hydrofluoric acid.

2. The method for efficiently recovering precious metals from waste automotive catalysts according to claim 1, characterized in that, The specific steps in S1 include: S11. The spent automotive catalyst is coarsely crushed and finely ground to obtain spent catalyst particles with a particle size ≤200 mesh. S12. Place the waste catalyst particles in a ball mill, introduce an inert atmosphere for protection, and ball mill at a low speed of 100r / min to 200r / min for 10min to 30min at a temperature of 80℃ to 120℃ to achieve pre-activation; S13. Increase the temperature to 150℃~200℃, increase the rotation speed to 200r / min~400r / min, add a composite activator accounting for 10%~30% of the mass of the waste automotive catalyst, and ball mill in an inert atmosphere for 10min~30min to achieve carrier pyrolysis. S14. Increase the temperature to 250℃~300℃, increase the rotation speed to 400r / min~600r / min, and maintain an inert atmosphere for ball milling for 30min~60min to achieve deep activation; S15. Keep inert atmosphere and cool to room temperature.

3. The method for efficiently recovering precious metals from waste automotive catalysts according to claim 2, characterized in that, In S12 to S15, the ball-to-material ratio is 15 to 25:

1.

4. The method for efficiently recovering precious metals from waste automotive catalysts according to claim 2, characterized in that, The composite activator comprises the following components by weight percentage: Sodium hydroxide 40%~60%, Sodium carbonate 20%~40%, Sodium nitrate 5%~15%, Zinc powder 5%~10%.

5. The method for efficiently recovering precious metals from waste automotive catalysts according to claim 2, characterized in that, The inert atmosphere is at least one of nitrogen or argon.

6. The method for efficiently recovering precious metals from waste automotive catalysts according to claim 2, characterized in that, In S12 to S14, the heating rate is 2℃ / min to 10℃ / min.

7. The method for efficiently recovering precious metals from waste automotive catalysts according to claim 6, characterized in that, The heating rate of S12 is 5℃ / min to 10℃ / min; the heating rate of S13 is 3℃ / min to 7℃ / min; and the heating rate of S14 is 2℃ / min to 5℃ / min.

8. The method for efficiently recovering precious metals from waste automotive catalysts according to claim 1, characterized in that, The steps in S3 specifically include: S31. Add the leaching precursor and leaching solvent to the reactor at a solid-liquid ratio of 1:3~6, and oxidize and leach for 30min~60min at a temperature of 90℃~95℃ and a rotation speed of 300r / min~500r / min. S32. Add stannous chloride to the reactor to a final concentration of 8 g / L to 12 g / L, and perform complexation leaching at a temperature of 90℃ to 95℃ and a rotation speed of 300 r / min to 500 r / min for 30 min to 60 min. S33. After leaching, filter while hot and collect the filtrate and filter residue separately. Wash the filter residue with dilute hydrochloric acid and combine the washing liquid with the filtrate to form the leachate.

9. A method for efficiently recovering precious metals from waste automotive catalysts according to claim 1 or 8, characterized in that, In the leaching solvent of S3, the concentration of hydrochloric acid is 4 mol / L to 8 mol / L, the concentration of nitric acid is 1 mol / L to 2 mol / L, and the concentration of hydrofluoric acid is 0.5 mol / L to 1.5 mol / L.

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