Method for recovering and preparing spheroidic platinum powder from platinum-containing catalytic waste

Abstract

The invention discloses a method for recovering and preparing spheroidic platinum powder from platinum-containing catalytic waste, which comprises the following steps: 1, soaking the platinum-containing catalytic waste in a hydrochloric acid solution, filtering for the first time, adding aqua regia solution into filter residues, heating and boiling, removing nitrate, filtering for the second time, adding excessive ammonia water into filtrate to generate precipitate, and drying to obtain platinum-containing catalytic waste; after filtering for three times, adding a hydrochloric acid solution into filtrate to obtain a high-purity platinum solution; and 2, preparing an ascorbic acid solution, pouring the ascorbic acid solution into the high-purity platinum solution, quickly cooling the high-purity platinum solution in liquid nitrogen, freeze-drying to obtain nano platinum powder, and sintering at low temperature to obtain the micron-sized spheroid platinum powder. According to the method, base metals, other impurities, carbon carriers and other impurity metals in the platinum-containing catalytic waste are removed step by step through acid dissolution and alkali complexing processes, then liquid nitrogen rapid freezing, freeze drying and low-temperature sintering are combined, the spherical morphology and high purity of the platinum powder are effectively controlled, the micron-sized spheroidic platinum powder is obtained, and the method is suitable for the field of conductive platinum slurry.

Description

Technical Field

[0001] The present invention belongs to the technical field of powder metallurgy, and particularly relates to a method for recovering and preparing spherical platinum powder from platinum-containing catalytic waste. Background Art

[0002] With the development of society, more and more industrial catalysts are used, resulting in a large amount of industrial-grade noble metal catalyst waste. The carbon-supported platinum alloy catalyst mainly contains platinum, nickel, cobalt, copper, and iron elements. Therefore, the recovery of catalysts and the reuse of noble metal elements are crucial. In addition, with the rapid development of modern technologies, especially high-end technologies such as electronic information and aerospace, thick film hybrid integrated circuits are widely used, and platinum electronic pastes are also widely used. Platinum metal has excellent electrical conductivity and catalytic performance, does not react with air or corrosive gases under any conditions, and can be sintered in air at its melting point without reacting, etc. Therefore, it is of great significance to directly recover platinum from waste platinum-containing carbon-supported catalysts and prepare spherical platinum powder required for electronic industrial platinum pastes.

[0003] The patent with the publication number CN108620600A discloses a method for preparing high-purity large specific surface platinum black. The process uses high-purity ammonium chloroplatinate (greater than 99.99%) as the raw material, and adopts atomization granulation method and microwave calcination reduction method to obtain high-purity high specific surface platinum black for fuel cells. The specific steps are as follows: (1) Atomization granulation: Using the above-mentioned high-purity (NH 2 PtCl 6 powder as the raw material, adopting spray drying method, controlling the liquid flow rate to be 3.0 mL / min - 8.0 mL / min, the atomization air pressure to be 0.1 MPa - 0.5 MPa, the inlet temperature to be 180°C - 220°C, the hot air flow rate to be 4.0 L / min - 10.0 L / min, and the solution concentration to be 0.01 mol / L - 1 mol / L, to obtain high-purity spherical (NH 4 ) 2 PtCl 6 particles; (2) Microwave calcination reduction: The high-purity spherical (NH 4 ) 2 PtCl 6Particles are placed in a microwave oven and calcined in two stages. In the first stage, under nitrogen protection, the heating rate is 5°C / min to 20°C / min, the temperature is raised to 400°C to 500°C, held for 1h to 4h, and cooled with the furnace. In the second stage, hydrogen reduction is carried out. Under hydrogen conditions, the heating rate is 10°C / min to 20°C / min, the temperature is raised to 500°C to 650°C, held for 1h to 4h, and cooled with the furnace. Platinum black is successfully prepared. This platinum powder can be used as a fuel cell electrode catalyst. Although this method has very good results in preparing platinum black with a large specific surface area, it is not suitable for recovering platinum from waste materials and preparing spherical platinum powder.

[0004] The patent with the publication number CN116673486A discloses a method for preparing highly dispersed platinum powder. In this method, a dispersant is first weighed and dissolved in deionized water in a reaction kettle as the reaction bottom liquid, a platinum salt solution is prepared as an oxidant, a reducing agent solution is prepared, and a sodium hydroxide solution with a corresponding mass fraction is prepared. Subsequently, the three reagents are added dropwise to the reaction kettle at a set flow rate for the preparation reaction; after the reaction is completed, coating is carried out, the solid-liquid phase is centrifuged and separated, and drying is carried out to obtain the final platinum powder product; by changing the sodium hydroxide concentration and adjusting the dropping flow rate, this invention can prepare platinum powder that does not require the addition of seeds, has adjustable particle size, and has high dispersibility. However, this method does not clearly put forward the performance indicators of the platinum powder, and it is not suitable for recovering platinum from waste materials and preparing platinum powder for electronic pastes.

[0005] The patent with the publication number CN116967460A discloses a method for preparing high-purity platinum powder from a platinum-rhodium alloy. This method includes the following steps: (1) Dissolve the platinum-rhodium alloy in aqua regia; (2) Add a platinum complexing agent, and platinum precipitates for the first time. Platinum and rhodium are separated by precipitation to obtain a platinum salt; (3) Targetedly dissolve the platinum salt 1 to obtain a platinum solution; (4) Oxidize the platinum solution to carry out secondary platinum precipitation to obtain platinum salt 2; (5) Platinum salt 2 is reduced and acid-treated to obtain ultra-high-purity platinum powder. This method mainly solves the problems of difficult purification of ultra-high-purity platinum powder, high requirements for raw materials, and cumbersome steps in the prior art, effectively recovers platinum and purifies it, but there is no constraint on the final form of platinum.

[0006] Therefore, there is an urgent need for a method for recovering and preparing spherical platinum powder from platinum-containing catalytic waste. Summary of the Invention

[0007] The technical problem to be solved by the present invention is to provide a method for recovering and preparing spherical platinum powder from platinum-containing catalytic waste in view of the above-mentioned deficiencies of the prior art. This method successively adopts an acid dissolution and alkali complexation process to stepwise remove base metals, other impurities, carbon carriers, and other impurity metals in the platinum-containing catalytic waste, convert the platinum element in the platinum catalytic waste into a high-purity platinum solution, and then combine liquid nitrogen rapid freezing, freeze drying, and low-temperature sintering to effectively control the spherical morphology and high purity of the platinum powder, and solve the problem of the lack of a preparation method for directly obtaining platinum powder for electronic pastes from waste materials in the prior art.

[0008] To solve the above technical problems, the technical solution adopted by the present invention is as follows: A method for recovering and preparing spherical platinum powder from platinum-containing catalytic waste, characterized in that the method comprises the following steps:

[0009] Step 1: Immerse the platinum-containing catalytic waste in a hydrochloric acid solution, filter it once, add aqua regia solution to the obtained filter residue and heat it to boiling, then carry out nitric acid expulsion, filter it twice, and add an excessive amount of ammonia water to the filtrate obtained by the second filtration to generate a precipitate. After filtering three times, add a hydrochloric acid solution to the obtained filtrate to obtain a high-purity platinum solution.

[0010] Step 2: Prepare an ascorbic acid solution and quickly pour it into the high-purity platinum solution obtained in Step 1, stir evenly, then quickly cool it in liquid nitrogen, obtain nano-platinum powder through freeze-drying, and then place the nano-platinum powder in a tube furnace for low-temperature sintering to obtain micron-sized spherical platinum powder.

[0011] Compared with the sponge-like platinum powder prepared by traditional recovery methods, further processes are required to prepare special platinum powder. Or the liquid-phase chemical synthesis method has disadvantages such as easy agglomeration, difficult cleaning of the dispersant, difficult control, and large amount of waste liquid when adding a reducing agent and a dispersant to the recovered platinum salt to prepare platinum powder. In the present invention, the platinum-containing catalytic waste is first immersed in a hydrochloric acid solution and filtered once. The hydrochloric acid is used to dissolve the base metals and other impurities in the platinum-containing catalytic waste, transfer them to the solution and remove them through the first filtration. Then, aqua regia solution is added to the obtained filter residue, heated to boiling and filtered twice. The aqua regia is used to completely dissolve the metallic platinum on the carbon carrier in the filter residue, and the residual carbon carrier in the filter residue is removed through the second filtration to obtain a filtrate, that is, a platinum solution. Then, an excessive amount of ammonia water is added to the platinum solution. The ammonia water is used to complex platinum ions, and other impurity metals form hydroxide precipitates and are removed through three filtrations to obtain an impurity-free high-purity platinum solution (usually, the mass purity of platinum in it is greater than 99.99%). Then, the present invention quickly pours the ascorbic acid solution into the high-purity platinum solution, mixes it evenly and quickly freezes it in liquid nitrogen to effectively prevent the growth and aggregation of nano-platinum powder. Then, freeze-drying is used to avoid the agglomeration of platinum nanoparticles to obtain uniformly dispersed nano-platinum powder. Then, through low-temperature sintering, the scale and morphology are regulated to effectively control the growth of nano-platinum powder to micron-sized and dense spherical platinum powder.

[0012] For the above-mentioned method for recovering and preparing spherical platinum powder from platinum-containing catalytic waste, it is characterized in that the concentration of the hydrochloric acid in Step 1 is 5wt% - 15wt%, the soaking time is 0.5h - 4h, and the heating time for adding aqua regia solution and heating to boiling is 1h. By controlling the concentration and time of hydrochloric acid soaking and the heating time for adding aqua regia for dissolution and heating to boiling, the base metals and other impurities and carbon carriers in the platinum-containing catalytic waste are effectively removed, so that the platinum element is concentrated in the tail liquid, that is, the filtrate obtained by the second filtration, ensuring the smooth preparation of the subsequent high-purity platinum solution.

[0013] In the above method for recovering and preparing spherical platinum powder from platinum-containing catalytic waste, it is characterized in that the volume of excessive ammonia water added to the filtrate obtained by the secondary filtration in step one is 1 to 2 times the volume of the filtrate, and hydrochloric acid solution is added to the filtrate obtained after the tertiary filtration until the pH is 2 to 5. By controlling the volume of excessive ammonia water and the degree of adding hydrochloric acid solution, trace impurity elements in the secondary filtration filtrate are effectively removed, ensuring the high purity of the subsequent platinum powder product.

[0014] In the above method for recovering and preparing spherical platinum powder from platinum-containing catalytic waste, it is characterized in that the concentration of the ascorbic acid solution in step two is 0.1 g / mL to 2 g / mL, the freeze-drying time is 12 h to 24 h, the temperature of the low-temperature sintering is 300 °C to 500 °C, and the heat preservation time is 0.5 h to 2 h. By controlling the concentration of the ascorbic acid solution, the freeze-drying time, and the parameters of the low-temperature sintering, the agglomeration phenomenon of the platinum powder is adjusted, effectively controlling the particle size of the platinum powder.

[0015] In the above method for recovering and preparing spherical platinum powder from platinum-containing catalytic waste, it is characterized in that the particle size of the micron-sized spherical platinum powder in step two is 0.5 μm to 5 μm, the specific surface area is less than 3 m 2 / g, the morphology is spherical, and the platinum mass content is 99.9%. The platinum powder with the above properties prepared by the present invention has good fluidity and viscosity after being made into a slurry, and is suitable for conductive slurries.

[0016] The present invention has the following advantages compared with the prior art:

[0017] 1. The present invention successively adopts the processes of hydrochloric acid immersion, aqua regia boiling, and ammonia complexation to stepwise remove base metals, other impurities, carbon carriers, and other impurity metals in the platinum-containing catalytic waste, convert the platinum element in the platinum catalytic waste into a high-purity platinum solution, and then combine the addition of ascorbic acid, rapid freezing with liquid nitrogen, freeze-drying, and low-temperature sintering to prevent the platinum powder from growing and agglomerating excessively, effectively controlling the growth of nano-platinum powder into micron-sized and dense spherical platinum powder, realizing the recovery of the platinum element in the platinum-containing catalytic waste.

[0018] 2. The preparation method of the present invention stably and effectively controls the morphology of the platinum powder, has a simple process, a high yield, a large output, and is easy to industrialize.

[0019] 3. The product platinum powder prepared by the present invention is spherical, with a particle size range of 0.5 μm to 5 μm, a specific surface area less than 3 m 2 / g, and the platinum mass content is 99.9%. It has high purity and can meet the requirements of conductive platinum slurries.

[0020] The technical solution of the present invention will be further described in detail below with reference to the drawings and embodiments. Brief Description of the Drawings

[0021] Figure 1 This is a flowchart for recovering and preparing spherical platinum powder from platinum-containing catalytic waste in the present invention.

[0022] Figure 2 This is a low-magnification SEM image of the spherical platinum powder prepared in Example 1 of the present invention.

[0023] Figure 3 This is a high-magnification SEM image of the spherical platinum powder prepared in Example 1 of the present invention. Detailed Description of the Invention

[0024] Example 1

[0025] As Figure 1 shown, this example includes the following steps:

[0026] Step 1: Immerse 100 g of platinum-containing catalytic waste in a hydrochloric acid solution with a concentration of 10 wt% for 4 h. After the first filtration, add aqua regia solution to the obtained filter residue and heat it to boiling for 1 h, then remove nitrates, perform the second filtration, and add an excessive amount of ammonia water with a concentration of 25% - 30% in a volume 2 times that of the filtrate to produce a precipitate. After the third filtration, add hydrochloric acid solution to the obtained filtrate until pH = 5 to obtain a high-purity platinum solution.

[0027] Step 2: Prepare an ascorbic acid solution with a concentration of 2 g / mL and quickly pour it into an equal volume of the high-purity platinum solution obtained in Step 1, stir evenly, then place it in liquid nitrogen for rapid cooling, and obtain nano-sized platinum powder after freeze-drying for 12 h. Then place the nano-sized platinum powder in a tube furnace for low-temperature sintering at a temperature of 400 °C and a holding time of 2 h to obtain micro-sized spherical platinum powder.

[0028] Figure 2 and Figure 3 are the low-magnification and high-magnification SEM images of the spherical platinum powder prepared in this example respectively. From Figure 2 and Figure 3 it can be seen that the microscopic morphology of the platinum powder prepared in this example is spherical powder, and the particle size distribution is uniform, with a particle size of 0.5 μm - 5 μm and a specific surface area of less than 3 m 2 / g; the mass content of platinum in the platinum powder is detected to be 99.9%.

[0029] Example 2

[0030] As Figure 1 shown, this example includes the following steps:

[0031] Step 1: Immerse 100 g of platinum-containing catalytic waste in a hydrochloric acid solution with a concentration of 5 wt% for 0.5 h. After primary filtration, add aqua regia solution to the obtained filter residue and heat it to boiling for 1 h. Then, carry out nitrate removal, secondary filtration, and add an excessive amount of ammonia water with a concentration of 25% - 30% and a volume twice that of the filtrate to produce a precipitate. After tertiary filtration, add hydrochloric acid solution to the obtained filtrate until the pH = 3 to obtain a high-purity platinum solution;

[0032] Step 2: Prepare an ascorbic acid solution with a concentration of 1 g / mL and quickly pour it into an equal volume of the high-purity platinum solution obtained in Step 1, stir evenly, then place it in liquid nitrogen for rapid cooling, and obtain nano-platinum powder after freeze-drying for 16 h. Then, place the nano-platinum powder in a tube furnace for low-temperature sintering at a temperature of 300 °C and a holding time of 2 h to obtain micro-scale spherical platinum powder.

[0033] After testing, the microscopic morphology of the platinum powder prepared in this example is spherical powder, and the particle size distribution is uniform, with a particle size of 1 μm - 4 μm and a specific surface area of less than 3 m 2 / g; After testing, the mass content of platinum in this platinum powder is 99.99%.

[0034] Comparing the platinum powder prepared in this example with that in Example 1, it can be seen that the particle size and dispersion of the platinum powder change little.

[0035] Example 3

[0036] As Figure 1 shown, this example includes the following steps:

[0037] Step 1: Immerse 100 g of platinum-containing catalytic waste in a hydrochloric acid solution with a concentration of 15 wt% for 4 h. After primary filtration, add aqua regia solution to the obtained filter residue and heat it to boiling for 1 h. Then, carry out nitrate removal, secondary filtration, and add an excessive amount of ammonia water with a concentration of 25% - 30% and a volume once that of the filtrate to produce a precipitate. After tertiary filtration, add hydrochloric acid solution to the obtained filtrate until the pH = 5 to obtain a high-purity platinum solution;

[0038] Step 2: Prepare an ascorbic acid solution with a concentration of 2 g / mL and quickly pour it into an equal volume of the high-purity platinum solution obtained in Step 1, stir evenly, then place it in liquid nitrogen for rapid cooling, and obtain nano-platinum powder after freeze-drying for 24 h. Then, place the nano-platinum powder in a tube furnace for low-temperature sintering at a temperature of 500 °C and a holding time of 2 h to obtain micro-scale spherical platinum powder.

[0039] After testing, the microscopic morphology of the platinum powder prepared in this example is spherical powder, and the particle size distribution is uniform, with a particle size of 2 μm - 6 μm and a specific surface area of less than 3 m 2 / g; After testing, the mass content of platinum in this platinum powder is 99.99%.

[0040] Example 4

[0041] As Figure 1 shown, this example includes the following steps:

[0042] Step 1: Immerse 100 g of platinum-containing catalytic waste in a hydrochloric acid solution with a concentration of 10 wt% for 2 h. After primary filtration, add aqua regia solution to the obtained filter residue and heat it to boiling for 1 h, then carry out nitrate removal, secondary filtration, and add 1.5 times the volume of excessive ammonia water with a concentration of 25% - 30% to the filtrate obtained from secondary filtration to generate precipitation. After tertiary filtration, add hydrochloric acid solution to the obtained filtrate until pH = 2 to obtain a high-purity platinum solution;

[0043] Step 2: Prepare an ascorbic acid solution with a concentration of 0.1 g / mL and quickly pour it into an equal volume of the high-purity platinum solution obtained in Step 1, stir evenly, then place it in liquid nitrogen for rapid cooling, and obtain nano-sized platinum powder after freeze-drying for 24 h. Then place the nano-sized platinum powder in a tube furnace for low-temperature sintering at a temperature of 400 °C and a holding time of 0.5 h to obtain micron-sized spherical-like platinum powder.

[0044] After detection, the microscopic morphology of the platinum powder prepared in this example is spherical-like powder, and the particle size distribution is uniform, with a particle size of 0.5 μm - 3 μm and a specific surface area of less than 3 m 2 / g; after detection, the mass content of platinum in this platinum powder is 99.99%.

[0045] Example 5

[0046] As Figure 1 shown, this example includes the following steps:

[0047] Step 1: Immerse 100 g of platinum-containing catalytic waste in a hydrochloric acid solution with a concentration of 8 wt% for 3 h. After primary filtration, add aqua regia solution to the obtained filter residue and heat it to boiling for 1 h, then carry out nitrate removal, secondary filtration, and add 1 times the volume of excessive ammonia water with a concentration of 25% - 30% to the filtrate obtained from secondary filtration to generate precipitation. After tertiary filtration, add hydrochloric acid solution to the obtained filtrate until pH = 4 to obtain a high-purity platinum solution;

[0048] Step 2: Prepare an ascorbic acid solution with a concentration of 0.5 g / mL and quickly pour it into an equal volume of the high-purity platinum solution obtained in Step 1, stir evenly, then place it in liquid nitrogen for rapid cooling, and obtain nano-sized platinum powder after freeze-drying for 12 h. Then place the nano-sized platinum powder in a tube furnace for low-temperature sintering at a temperature of 300 °C and a holding time of 1 h to obtain micron-sized spherical-like platinum powder.

[0049] Upon detection, the microscopic morphology of the platinum powder prepared in this example is spherical-like powder, and the particle size distribution is uniform, with a particle size of 0.5 μm to 4 μm, and the specific surface area is less than 3 m 2 / g; upon detection, the mass content of platinum in the platinum powder is 99.99%.

[0050] Example 6

[0051] As Figure 1 shown, this example includes the following steps:

[0052] Step 1: Immerse 100 g of platinum-containing catalytic waste in a hydrochloric acid solution with a concentration of 15 wt% for 4 h. After primary filtration, add aqua regia solution to the obtained filter residue and heat it to boiling for 1 h, then carry out nitrate removal, secondary filtration, and add 1.5 times the volume of excessive ammonia water with a concentration of 25% - 30% to the filtrate obtained from the secondary filtration to generate precipitation. After tertiary filtration, add hydrochloric acid solution to the obtained filtrate until pH = 3 to obtain a high-purity platinum solution;

[0053] Step 2: Prepare an ascorbic acid solution with a concentration of 2 g / mL and quickly pour it into an equal volume of the high-purity platinum solution obtained in Step 1, stir evenly, then place it in liquid nitrogen for rapid cooling, freeze-dry for 20 h to obtain nano-sized platinum powder, and then place the nano-sized platinum powder in a tube furnace for low-temperature sintering at a temperature of 400 °C and a holding time of 1 h to obtain micron-sized spherical-like platinum powder.

[0054] Upon detection, the microscopic morphology of the platinum powder prepared in this example is spherical-like powder, and the particle size distribution is uniform, with a particle size of 0.5 μm to 5 μm, and the specific surface area is less than 3 m 2 / g; upon detection, the mass content of platinum in the platinum powder is 99.99%.

[0055] Comparing the platinum powder prepared in this example with that in Example 1, it can be seen that the particle size and dispersibility of the platinum powder change little.

[0056] The above are only the preferred embodiments of the present invention and do not impose any limitations on the present invention. Any simple modifications, changes, and equivalent variations made to the above embodiments according to the technical essence of the invention still fall within the protection scope of the technical solution of the present invention.

Claims

1. A method for recovering and preparing spherical platinum powder from platinum-containing catalytic waste, characterized in that: The method comprises the following steps: Step 1: Soak the platinum-containing catalytic waste in a hydrochloric acid solution, add aqua regia solution to the filter residue obtained after the first filtration and heat to boil, then remove nitrate, filter twice, add excess ammonia water to the filtrate obtained by the second filtration to produce precipitation, add hydrochloric acid solution to the filtrate obtained after the third filtration to obtain a high-purity platinum solution; Step 2: prepare an ascorbic acid solution and quickly pour it into the high-purity platinum solution obtained in step 1 and stir it evenly, then place it in liquid nitrogen for rapid cooling, freeze-dry to obtain nano-platinum powder, and then place the nano-platinum powder in a tubular furnace for low-temperature sintering to obtain micron-sized spherical platinum powder.

2. The method for recovering and preparing spherical platinum powder from platinum-containing catalytic waste according to claim 1, characterized in that: In step 1, the concentration of the hydrochloric acid is 5wt% to 15wt%, the soaking time is 0.5h to 4h, and the time for heating and boiling the aqua regia solution is 1h.

3. The method for recovering and preparing spherical platinum powder from platinum-containing catalytic waste according to claim 1, characterized in that: The volume of excess ammonia water added to the filtrate obtained by the secondary filtration in step 1 is 1 to 2 times the volume of the filtrate, and hydrochloric acid solution is added to the filtrate obtained after the tertiary filtration until the pH value is 2 to 5.

4. The method for recovering and preparing spherical platinum powder from platinum-containing catalytic waste according to claim 1, characterized in that: The concentration of the ascorbic acid solution in step 2 is 0.1 g / mL to 2 g / mL, the freeze-drying time is 12 h to 24 h, the low-temperature sintering temperature is 300° C. to 500° C., and the insulation time is 0.5 h to 2 h.

5. The method for recovering and preparing spherical platinum powder from platinum-containing catalytic waste according to claim 1, characterized in that: The micron-sized spherical platinum powder in step 2 has a particle size of 0.5 μm to 5 μm and a specific surface area of ​​less than 3 m 2 / g, the shape is spherical, and the platinum mass content is 99.9%.

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