CN110055423B - A method for enriching platinum group metals and rare earths in failed automobile exhaust gas purification catalysts - Google Patents

Abstract

The invention relates to a method for enriching platinum group metals and rare earth in a spent automobile exhaust purification catalyst, which is characterized in that the spent automobile exhaust purification catalyst is finely ground and then is subjected to pressure leaching in a sodium hydroxide solution, so that gamma-A1 in the spent automobile exhaust purification catalyst is obtained₂O₃Partially dissolving and converting the cordierite carrier in the catalyst into sodalite which is easily dissolved in an acid system; the produced pressure leaching slag is subjected to acid leaching, rare earth elements enter the acid leaching solution, and platinum, palladium and rhodium elements are retained in the slag, so that the separation of platinum, palladium, rhodium and rare earth is realized; and adding sodium sulfate into the acidic leaching solution to form sulfuric acid rare earth compound salt precipitate, recovering rare earth elements, and further treating the acidic insoluble slag to recover platinum, palladium and rhodium metal. The leaching rate of lanthanum and yttrium reaches more than 95%, platinum, palladium and rhodium in the spent automobile exhaust purification catalyst are enriched by more than 13 times, subsequent extraction of noble metals is facilitated, and the comprehensive recovery rate of lanthanum and yttrium reaches more than 90%.

Description

A method for enriching platinum group metals and rare earths in failed automobile exhaust gas purification catalysts

technical field

The invention relates to a hydrometallurgical process in the metallurgical field, and is a method for effectively enriching platinum group metals and rare earths in a catalyst for purifying the exhaust gas of a failed automobile.

Background technique

Autocatalysts are an important way to control vehicle exhaust emissions and reduce pollution in the fuel locomotive industry. The current mainstream auto catalysts are composed of carriers (2MgO·2A1 ₂ O ₃ ·5SiO ₂ or 2FeO·2A1 ₂ O ₃ ·0.5SiO ₂ ), surface coatings (γ-A1 ₂ O ₃ ), active materials (Pt, Pd and Rh) and additives (Ce, La, Ba, Sr, Zr and other rare earth or alkaline earth element oxides), the content of precious metals is generally more than 0.05%, and about 4% to 8% of rare earth elements. At present, the annual output of platinum group metals in the world is about 300t, of which 90% comes from countries such as Russia and South Africa. The reserves and output of platinum group metals in my country are very small, less than 1% of the world's output. Effective recovery of platinum group metals from secondary resources is one of the effective ways to solve the problem of resource shortage. Therefore, it is of great significance to study the recovery of platinum group metals and rare earths from failed auto catalysts.

According to the difference in chemical composition and properties of catalysts, many researchers have proposed different treatment methods to recover valuable metals in automobile exhaust purification catalysts. There are some methods to recover valuable metals by adding flux and oxidant and mixing with auto catalysts, and leaching after high temperature calcination; also recovering valuable metals by sulfating and roasting; for metal carrier auto catalysts, there are methods for recycling by high temperature smelting. valence metal.

In the invention patent CN102899498A (Zhang Zebiao, et al. A method for leaching platinum group metals from a defunct automobile exhaust gas purification catalyst. China, 201210368339.8[P].2013-01-30), the defunct catalyst is pulverized and finely ground, and then a flux is added. (NaHSO ₄ ) and oxidant (NaClO or NaClO ₃ ), mixed uniformly and calcined at high temperature, then the calcined product was immersed in water at room temperature, and the filter residue was added to oxidant (H ₂ O ₂ ) and hydrochloric acid for acid leaching, filtered and washed to obtain platinum group metal containing platinum A solution of palladium and rhodium. The invention has a high leaching rate for platinum group metals, especially the leaching rate of rhodium element reaches more than 99%, but the content of impurity elements in the solution is high, and subsequent separation and extraction are difficult, and cannot be effectively used.

In the invention patent CN105671304A (Dong Haigang, et al. A method for recovering rare earths and platinum group metals from a failed automobile exhaust gas purification catalyst. China, 201610102182.2 [P]. 2016-06-15), the spent automobile exhaust gas purification catalyst is finely ground After that, it is mixed with sulfuric acid for sulfation roasting, and then acid leaching is performed with dilute sulfuric acid, rare earth elements are recovered from the acid leaching solution, and platinum group metals are recovered from the acid leaching residue. The invention adopts the method of sulfidation and roasting to recover valuable metals, and the operation environment is poor, and the pollution to the environment is serious.

In the invention patent CN106282568A (Fan Xingxiang, et al. A method for enriching platinum group metals from a metal carrier of a failed automobile exhaust catalyst. China, 201510285196.8 [P]. 2017-01-04), the use of high temperature melting failed automobile exhaust gas purification catalysts , and then cooled or atomized and sprayed to form fine alloys, and then acid is added to selectively leaching alkali metals. After filtration and washing, platinum group metal concentrates are obtained to achieve high-efficiency enrichment of platinum group metals. This invention does not need to add any additional collector, and the operation is simple, but it needs to use a high-temperature melting furnace such as a plasma electric furnace, which requires a large amount of energy consumption. At the same time, this method has certain limitations. Additional collectors need to be added to extract the valuable metals.

SUMMARY OF THE INVENTION

The object of the present invention is to provide a method for efficiently enriching platinum, palladium, rhodium and rare earth elements in the exhaust gas purification catalyst of an invalid vehicle.

The technical scheme adopted by the present invention in order to achieve the above-mentioned purpose is: after finely grinding the defunct automobile exhaust gas purification catalyst, pressurized leaching is carried out in sodium hydroxide solution, so that the γ-A1 ₂ O ₃ in it is partially dissolved and the cordierite in the catalyst is dissolved. The carrier is converted into sodalite, which is easily soluble in the acidic system; the produced pressurized leaching slag is subjected to acid leaching, the rare earth elements enter the acidic leaching solution, and the platinum, palladium and rhodium elements remain in the slag to realize the separation of platinum, palladium, rhodium and rare earth. ; Add sodium sulfate to the acid leaching solution to form a rare earth sulfate compound salt precipitation, thereby recovering rare earth elements, and the acid insoluble slag is further processed to recover metals such as platinum, palladium, and rhodium.

The specific process and technical parameters are as follows:

1. Pressurized alkaline immersion

The failed automobile exhaust gas purification catalyst is crushed and finely ground to a particle size range of less than 0.149mm, and then the ground spent catalyst is mixed with sodium hydroxide solution and then added to the autoclave. The sodium hydroxide is added for quality control as the failed automobile exhaust gas purification catalyst. 0.5~3.0 times of the mass, the liquid-solid ratio (the ratio of liquid volume mL to the mass g of the failed automobile exhaust purification catalyst) is 3~8:1, the stirring speed is 300~600rpm, heated to 150~250℃, and the reaction is 2~4h After the reaction is completed, after filtration and washing, pressure leaching solution and pressure leaching residue are obtained.

2. Pickling

Acid leaching the pressurized leaching residue with 1.0~4.0mol/L hydrochloric acid solution to control the liquid-solid ratio (the ratio of the liquid volume mL to the mass g of the pressurized leaching residue) to be 5~15:1, and then add the reducing agent hydrazine hydrate to hydrate The volume fraction of hydrazine is controlled to be 0.1%~0.5% of the solution volume, the acid leaching time is 0.5~4.0h, the acid leaching temperature is 50~90°C, and the stirring speed is 300~600rpm; after the reaction, the acid leaching is obtained after filtration and washing. Leachate and acid leaching insoluble residue; acid leaching leaching solution is used to recover rare earth elements, and acid leaching insoluble residue is used to further recover platinum group metal elements.

3. Double salt precipitation

Add sodium hydroxide to the acid leaching solution to adjust the pH of the solution to 0.5~3.0, then add sodium sulfate, control the quality of sodium sulfate to be 3~10:1 of the rare earth mass in the solution, the reaction temperature is 50~70 ℃, the reaction time It is 15~60min, and the stirring speed is 300~600rpm. Filtration, washing and drying are carried out to obtain the precipitate of rare earth sulfate double salt.

The sodium hydroxide, sodium sulfate, hydrochloric acid and hydrazine hydrate are all industrial grade reagents.

In the defunct automobile exhaust gas purification catalyst, mass content: Al 5.0%-30.0%, Si 5.0%-30.0%, La 0.1%-5.0%, Y 0.01%-2.0%, Ce 1.0%-15.0%, Pt 20.0 ~500.0g/t, Pd 30.0~800.0g/t, Rh5.0~300.0g/t.

Compared with the traditional recovery and treatment method of the exhausted automobile exhaust gas purification catalyst, the invention has the following advantages: (1) pressure leaching can convert the insoluble cordierite carrier in the catalyst into the sodalite which is easily soluble in the acid system, and the pressure leaching residue When leaching with hydrochloric acid solution, the leaching rate of aluminum and silicon is more than 94%, and the leaching rate of lanthanum and yttrium is more than 95%, which enriches the platinum, palladium and rhodium in the failed automobile exhaust gas purification catalyst by more than 13 times, which is beneficial to the subsequent extraction of precious metals. (2) The recovery of rare earth elements can be achieved by acid leaching and double salt precipitation, among which the comprehensive recovery rate of lanthanum and yttrium elements reaches more than 90%; (3) The alkaline pressure leaching has little corrosion to the equipment, safe operation, and valuable The comprehensive recovery benefit of metals is good; (4) the present invention has low labor intensity, short processing time and good operating environment.

Description of drawings

Figure 1: Process flow diagram of the present invention.

Detailed ways

Example 1

The specific components of the catalyst: Al 17.97%, Si 17.78%, La 0.58%, Y 0.28%, Ce 4.02%, Pt 113.5g/t, Pd 212g/t, Rh 73g/t.

Technical grade sodium hydroxide, its NaOH content is ≥96%; technical grade sodium _sulfate , its _Na2SO4 content is ≥96%; technical grade hydrochloric acid, its HCl content is 36%~38%; technical grade hydrazine hydrate, its _N2 The H ₄ ·H ₂ O content is ≥80%.

Take 15.00g of the invalid automobile exhaust purification catalyst with a particle size of less than 0.149mm after fine grinding, mix it with 12.00g of sodium hydroxide, add it to the autoclave, then add 75mL of deionized water, control the stirring speed to 400rpm, and slowly heat it to 150℃ , the reaction was carried out for 3.0h; after the reaction was completed, filtration and washing were performed to obtain 200mL of pressurized leaching solution and 19.03g of pressurized leaching residue. The components of the pressurized leaching solution are: Si 2.38g/L, Al 2.47g/L, La 9.50mg/L, Y 2.50mg/L, Ce 10.00mg/L, and the content of platinum, palladium and rhodium is basically zero. The slag rate of pressure leaching was 126.87%, and the leaching rates of cerium, lanthanum and yttrium were 0.33%, 2.18% and 1.19%, respectively.

Take 10.00 g of the above pressure leaching residue, pickle it with 150 mL of 1.5 mol/L hydrochloric acid solution, add 0.15 mL of hydrazine hydrate, the acid leaching time is 2 h, the acid leaching temperature is 80 °C, and the stirring speed is 400 rpm; after the reaction is completed, filter, After washing, 250 mL of acid leaching leaching solution and 1.01 g of acid leaching insoluble residue were obtained. The components of the acid leaching solution are: Al 4.38g/L, Si 4.37g/L, La 170.48mg/L, Y 83.63mg/L, Ce 404.87mg/L. The acid leaching insoluble slag rate was 10.10%, the leaching rates of aluminum and silicon were 94.85% and 94.63%, and the leaching rates of lanthanum and yttrium were 95.30% and 95.87%, respectively; platinum, palladium and rhodium were basically enriched in acid leaching insoluble In the slag, they were enriched by 13.74 times, 13.61 times and 13.58 times, respectively. The acid leaching insoluble residue further extracts platinum group metals.

Take 200 mL of acid leaching solution, add an appropriate amount of sodium hydroxide to it until the pH of the solution is 2.0, then add 0.70 g of sodium sulfate, the reaction temperature is 50 ° C, the stirring speed is 300 rpm, and the reaction time is 15 min. After completion of the reaction, filter and wash to obtain 300 mL of filtrate and 0.41 g of precipitate. The composition of the filtrate is: La 3.40mg/L, Y 1.40mg/L, Ce 6.93mg/L, and the precipitation rates of cerium, lanthanum and yttrium are 97.66%, 97.01% and 97.49% respectively. The comprehensive recoveries of lanthanum and yttrium were 92.48% and 93.42%, respectively.

Example 2

The specific components of the catalyst: Si 17.82%, Al 17.94%, La 0.60%, Y 0.29%, Ce 4.12%, Pt 115.4g/t, Pd 221.5g/t, Rh 78.2g/t.

Technical grade sodium hydroxide, its NaOH content is ≥96%; technical grade sodium _sulfate , its _Na2SO4 content is ≥96%; technical grade hydrochloric acid, its HCl content is 36%~38%; technical grade hydrazine hydrate, its _N2 The H ₄ ·H ₂ O content is ≥80%.

Take 15.00g of ineffective automobile exhaust purification catalyst with a particle size of less than 0.149mm after fine grinding, mix it with 30.00g of sodium hydroxide, add it to the autoclave, then add 90mL of deionized water, control the stirring speed to 600rpm, and slowly heat it to 200°C , the reaction was 4.0h; after the reaction, 200mL of pressurized leaching solution and 19.06g of pressurized leaching residue were obtained by filtration and washing. The components of the pressurized leaching solution are: Al 2.45g/L, Si 2.41g/L, La 9.98mg/L, Y 3.01mg/L, Ce 14.98mg/L, and the content of platinum, palladium and rhodium is basically zero. The slag rate of pressure leaching was 127.07%, and the leaching rates of cerium, lanthanum and yttrium were 0.49%, 2.22% and 1.38%, respectively.

Take 10.00 g of the above-mentioned pressure leaching residue, pickle it with 100 mL of 3.0mol/L hydrochloric acid solution, add 0.50 mL of hydrazine hydrate, the acid leaching time is 1.5 h, the acid leaching temperature is 60 °C, and the stirring speed is 600 rpm; after the reaction is completed, filter and washing to obtain 250 mL of acid leaching leaching solution and 1.03 g of acid leaching insoluble residue. The components of the acid leaching solution are: Al 4.37g/L, Si 4.36g/L, La175.48mg/L, Y 85.63mg/L, Ce 448.26mg/L. The acid leaching insoluble residue rate was 10.30%, the leaching rates of aluminum and silicon were 94.67% and 94.84%, and the leaching rates of lanthanum and yttrium were 95.02% and 95.11%; platinum, palladium and rhodium were basically enriched in the acid leaching insoluble residue , the enrichment times were 13.52 times, 13.48 times and 13.94 times, respectively. The acid leaching insoluble residue further extracts platinum group metals.

Take 200 mL of acid leaching solution, add an appropriate amount of sodium hydroxide to it until the pH of the solution is 2.2, then add 1.00 g of sodium sulfate, the reaction temperature is 60 ° C, the stirring speed is 500 rpm, and the reaction time is 20 min. After completion of the reaction, filter and wash to obtain 300 mL of filtrate and 0.43 g of precipitate. The composition of the filtrate is: La 3.41mg/L, Y 1.50mg/L, Ce 8.62mg/L, and the precipitation rates of cerium, lanthanum and yttrium are 97.12%, 97.09% and 97.37%. The comprehensive recoveries of lanthanum and yttrium were 92.29% and 92.58%.

Claims (3)

1. A method for enriching platinum group metals and rare earth in a spent automobile exhaust purification catalyst is characterized by comprising the following steps:

A. pressure alkaline leaching

Crushing and finely grinding the spent automobile exhaust purification catalyst to be less than 0.149mm, then mixing the ground spent catalyst with a sodium hydroxide solution, adding the mixture into a high-pressure reaction kettle, wherein the mass of the sodium hydroxide is controlled to be 0.5-3.0 times of the mass of the spent automobile exhaust purification catalyst, the liquid-solid ratio, namely the ratio of the liquid volume m L to the mass g of the spent automobile exhaust purification catalyst, is 3-8: 1, the stirring speed is 300-600 rpm, heating is carried out to 150-250 ℃, and the reaction is carried out for 2-4 hours;

B. acid leaching

Acid leaching the pressure leaching slag with 1.0-4.0 mol/L hydrochloric acid solution, controlling the liquid-solid ratio, namely the ratio of the liquid volume m L to the weight g of the pressure leaching slag is 5-15: 1, then adding a reducing agent hydrazine hydrate, wherein the volume fraction of the hydrazine hydrate is 0.1-0.5% of the volume of the solution, the acid leaching time is 0.5-4.0 h, the acid leaching temperature is 50-90 ℃, the stirring speed is 300-600 rpm, filtering and washing after the reaction is finished to obtain acid leaching leachate and acid leaching insoluble slag, wherein the acid leaching leachate is used for recovering rare earth elements, and the acid leaching insoluble slag is used for further recovering platinum group metal elements;

C. precipitation of double salts

Adding sodium hydroxide into the acid leaching solution to adjust the pH value of the solution to 0.5-3.0, adding sodium sulfate, and controlling the mass of the sodium sulfate to be 3-10 of the mass of the rare earth in the solution: 1, the reaction temperature is 50-70 ℃, the reaction time is 15-60 min, the stirring speed is 300-600 rpm, and the rare earth sulfate double salt precipitate is obtained by filtering, washing and drying.

2. The method for enriching platinum group metals and rare earths in spent automotive exhaust gas purification catalysts according to claim 1, characterized in that: the sodium hydroxide, the sodium sulfate, the hydrochloric acid and the hydrazine hydrate are all industrial reagents.

3. The method for enriching platinum group metals and rare earth in the spent automobile exhaust purification catalyst according to claim 1, wherein the spent automobile exhaust purification catalyst comprises, by mass, 5.0-30.0% of Al, 5.0-30.0% of Si, 0.1-5.0% of L a, 0.01-2.0% of Y, 1.0-15.0% of Ce, 20.0-500.0 g/t of Pt, 30.0-800.0 g/t of Pd and 5.0-300.0 g/t of Rh.

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