A method for preparing high-uniformity micron-sized platinum powder

Abstract

The invention discloses a method for preparing a highly uniform micron-sized platinum powder. The method achieves the redox potential of a platinum powder preparation system by reducing sodium chloroplatinate with hydrazine hydrate by changing pH. The prepared platinum powder has a uniform spherical morphology, a controllable particle size, a narrow particle size distribution, does not require screening, and does not introduce impurities, thereby ensuring the purity of the prepared platinum powder. The method of the invention also has the advantages of being simple, fast, and having a low loss rate.

Description

Technical Field

[0001] The invention belongs to the technical field of preparing precious metal powder materials by hydrometallurgy, and particularly relates to a method for preparing micron-grade platinum powder with high uniformity. Background Art

[0002] Platinum powder has excellent electrical conductivity, thermal conductivity, chemical stability, and unique catalytic activity, optics, magnetism and other properties. It is widely used in important fields such as semiconductor devices, automotive industry, integrated circuits and precision alloys. With the rapid development of high-end manufacturing, the demand for platinum powder is increasing, and performance requirements are also getting higher and higher.

[0003] At present, the preparation method of platinum powder mainly adopts liquid phase chemical reduction method, which can be carried out under normal temperature and pressure conditions, requires simple equipment, has low production cost, simple process, and is suitable for large-scale production. However, in the preparation process, factors such as platinum precursor concentration, reducing agent type and concentration, dispersant type and concentration, reaction system temperature and pH, and material mixing method will affect the morphology, particle size distribution and dispersibility of the prepared platinum powder; due to the many influencing factors, if they cannot be effectively regulated, the platinum powder prepared by this method generally has problems such as diverse and uneven particle morphology, wide particle size distribution, and insufficient dispersion, resulting in poor consistency and continuity of products made from this raw material, which is difficult to meet application requirements; subsequent screening and grading processes are required to obtain qualified powders, and the subsequent screening and grading processes not only increase the operation process, but also cause waste of precious metal platinum powder, and introduce unnecessary impurities, reduce purity and other problems. Summary of the invention

[0004] The purpose of the present invention is to provide a method for preparing micron-sized platinum powder with high uniformity in view of the deficiencies of the prior art. The redox potential of the platinum powder system prepared by reducing sodium chloroplatinate with hydrazine hydrate is regulated by changing the pH value, and the prepared platinum powder has a uniform spherical morphology, controllable particle size, narrow particle size distribution, no need for screening, no impurities introduced, and the purity of the prepared platinum powder is ensured. The preparation method also has the advantages of being simple, fast, and having a low loss rate.

[0005] The technical solution of the present invention:

[0006] The preparation of high uniformity micron-sized platinum powder includes the following steps:

[0007] S1. Under room temperature, add a sodium chloroplatinate aqueous solution with a concentration of 1g-10g / L to a hydrazine hydrate solution with a concentration of 1%-5%, stir thoroughly, and test in real time to adjust the pH value of the reaction system to 5-10; the dripping rate of the sodium chloroplatinate aqueous solution is 1.0ml / min-10.0ml / min, and a peristaltic pump is used to control the dripping rate of the sodium chloroplatinate aqueous solution. The present invention uses a peristaltic pump to accurately control the dripping rate of the sodium chloroplatinate aqueous solution, and uses an electric stirrer to ensure that the stirring of the entire reaction process is stable and the materials are fully mixed, which is convenient for accurately testing the pH value of the reaction system;

[0008] S2. After the addition of the aqueous sodium chloroplatinate solution is completed, the solution is stirred for 20min-30min, maintaining the pH value of the reaction system at 5-10 to obtain platinum powder;

[0009] S3. The obtained platinum powder is repeatedly washed with deionized water, precipitated, and desalted until the pH of the reaction system is neutral, and then washed with anhydrous ethanol to remove water, and the soluble salts as byproducts in the liquid phase reduction system are removed by washing to improve the purity of the prepared platinum powder;

[0010] S4. The desalted and dehydrated platinum powder is vacuum dried to obtain micron-sized platinum powder with good uniformity, narrow particle size distribution, and D90-D10 < 3.1 μm. The present invention removes anhydrous ethanol in the washed platinum powder by vacuum drying, which can reduce the drying temperature, increase the volatilization rate, and reduce the agglomeration of platinum powder particles during the drying process.

[0011] The volume ratio of the sodium chloroplatinate aqueous solution to the hydrazine hydrate aqueous solution in step S1 is 1:0.2-2.

[0012] The stirring in step S1 is performed using an electric stirrer with a stirring speed of 100 r / min-500 r / min.

[0013] In step S1, the pH value of the reaction system is adjusted by using a sodium hydroxide aqueous solution or a hydrochloric acid aqueous solution with a mass concentration of 1%-2%, and the error range of the pH value is ±0.1.

[0014] The method for judging the desalination in step S3 is as follows: take the supernatant after repeated washing and precipitation with deionized water, measure the pH value to be 6.5-7.5, take 2-3 drops of 5% silver nitrate by mass and add them to the supernatant, and observe that there is no white precipitate, which means that the soluble salt has been removed.

[0015] The vacuum drying conditions in step S4 are as follows: temperature 60°C-90°C, vacuum degree 0.08MPa, and drying time 12h-24h.

[0016] Sodium chloroplatinate is the precursor and hydrazine hydrate is the reducing agent.

[0017] The beneficial effects of the present invention are: micron-sized platinum powder is prepared by a chemical liquid phase reduction method, and the redox potential of sodium chloroplatinate reduced by hydrazine hydrate is changed by adjusting the pH value of the reaction system (the redox potential in an alkaline environment is greater than that in an acidic environment), thereby regulating the redox reaction rate; at the same time, the pH of the reaction system is monitored and adjusted in real time and kept stable, so that the reduction, nucleation and growth processes of platinum particles are carried out in a stable pH environment. The method of the present invention can prepare highly uniform platinum powder, and also has the advantages of simple operation process, low equipment requirements and improved processing efficiency.

[0018] The applicant's experiments show that compared with an acidic environment, the redox potential in an alkaline environment is high, the reaction rate is large, and the particle size distribution of the prepared platinum powder is small; the platinum powder prepared by the method described in the present invention is uniformly spherical, D10=0.5μm-1.8μm, D50=1.9μm-3.0μm, D90=3.2μm-4.8μm, the particle distribution is uniform, and the particle size distribution is concentrated (D90-D10<3.1μm), and the particle size of the platinum powder can be effectively adjusted by controlling the pH of the hydrazine hydrate liquid phase reduction process of sodium chloroplatinate. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 The particle size distribution and microscopic morphology of platinum powder prepared under pH=9 conditions (magnification 10,000 times);

[0020] Figure 2 The particle size distribution and microscopic morphology of platinum powder prepared under pH=7 conditions (magnification 10000 times);

[0021] Figure 3 Particle size distribution and microscopic morphology of platinum powder prepared under pH=6 conditions (magnification 10,000 times). Specific implementation methods Embodiment 1:

[0022] This embodiment uses a liquid phase chemical reduction system to prepare platinum powder, which specifically includes the following steps:

[0023] S1. The precursor sodium chloroplatinate is prepared into an aqueous solution having a platinum content of 10 g / L, and the reducing agent hydrazine hydrate is prepared into an aqueous solution having a mass concentration of 1%;

[0024] S2. The sodium chloroplatinate aqueous solution was added dropwise to the hydrazine hydrate solution at room temperature, and the solution was stirred thoroughly during the addition; the dropping rate of the sodium chloroplatinate aqueous solution was controlled by a peristaltic pump to be 2.5 ml / min, the volume ratio of the sodium chloroplatinate aqueous solution to the hydrazine hydrate aqueous solution was 1: 2, and an electric stirrer was used for stirring at a stirring speed of 300 r / min;

[0025] S3. During the preparation of platinum powder, a pH meter is used to test the pH value of the liquid phase reaction system in real time, and an aqueous sodium hydroxide solution and an aqueous hydrochloric acid solution are used to adjust the pH value of the reaction system so that the pH of the reaction system remains stable within the range of pH = 9 ± 0.1;

[0026] S4. After the addition of the sodium chloroplatinate aqueous solution is completed, stirring is continued for 30 minutes, and the pH of the reaction system is tested in real time, and the pH of the reaction system is adjusted to 9 using an aqueous sodium hydroxide solution and an aqueous hydrochloric acid solution to keep it stable; in steps S3 and S4, the pH value of the reaction system is tested using a pH meter, and a 1% sodium hydroxide aqueous solution and a 1% hydrochloric acid aqueous solution are added dropwise to adjust the pH of the reaction system to within the range of 9±0.1;

[0027] S5. The reduced platinum powder in step S4 is repeatedly washed and precipitated with deionized water to remove soluble salts until the pH is neutral. After it is determined that the soluble salts are completely removed, it is washed twice with anhydrous ethanol to remove water; the platinum powder prepared by liquid phase reduction is repeatedly washed and precipitated with deionized water, and after the pH of the supernatant is tested to be 6.5-7.5, 2-3 drops of 5% silver nitrate by mass are added to the supernatant, and no white precipitate is observed to remove the soluble salts;

[0028] S6. The platinum powder which has been completely desalted and dehydrated in step S5 is vacuum dried at a temperature of 60°C-90°C and a vacuum degree of 0.08 MPa for 20 hours.

[0029] The platinum powder prepared by this method has high sphericity and uniform particle size distribution (see Figure 1 ), particle size D10=0.83μm, D50=1.91μm, D90=3.43μm, and D90-D10=2.6μm. Embodiment 2:

[0030] S1 and S2 are the same as in Example 1;

[0031] S3. During the preparation of platinum powder, a pH meter is used to test the pH value of the liquid phase reaction system in real time, and an aqueous sodium hydroxide solution and an aqueous hydrochloric acid solution are used to adjust the pH value of the reaction system so that the pH of the reaction system remains stable within the range of pH = 7 ± 0.1;

[0032] S4. After the addition of the sodium chloroplatinate aqueous solution is completed, stirring is continued for 30 minutes, and the pH of the reaction system is tested in real time, and the pH of the reaction system is adjusted to 7 using an aqueous sodium hydroxide solution and an aqueous hydrochloric acid solution to keep it stable; in steps S3 and S4, the pH value of the reaction system is tested using a pH meter, and a 1% sodium hydroxide aqueous solution and a 1% hydrochloric acid aqueous solution are added dropwise to adjust the pH of the reaction system to within the range of 7±0.1;

[0033] S5 and S6 are the same as in Example 1.

[0034] The platinum powder prepared by this method has high sphericity and uniform particle size distribution (see Figure 2 ), particle size D10=1.24μm, D50=2.35μm, D90=3.81μm, and D90-D10=2.63μm. Embodiment 3:

[0035] S1 and S2 are the same as in Example 1;

[0036] S3. During the preparation of platinum powder, a pH meter is used to test the pH value of the liquid phase reaction system in real time, and an aqueous sodium hydroxide solution and an aqueous hydrochloric acid solution are used to adjust the pH value of the reaction system so that the pH of the reaction system remains stable within the range of pH = 6 ± 0.1;

[0037] S4. After the addition of the sodium chloroplatinate aqueous solution is completed, stirring is continued for 30 minutes, and the pH of the reaction system is tested in real time, and the pH of the reaction system is adjusted to 6 using an aqueous sodium hydroxide solution and an aqueous hydrochloric acid solution to keep it stable; in steps S3 and S4, the pH value of the reaction system is tested using a pH meter, and a sodium hydroxide aqueous solution with a mass concentration of 1% and an aqueous hydrochloric acid solution with a mass concentration of 1% are added dropwise to adjust the pH of the reaction system to within the range of 6±0.1;

[0038] S5 and S6 are the same as in Example 1.

[0039] The platinum powder prepared by this method has high sphericity and uniform particle size distribution (such as the attached Figure 3 As shown), particle size D10=1.63μm, D50=2.86μm, D90=4.67μm, and D90-D10=3.04μm.

Claims

1. A method for preparing high-uniformity micron-sized platinum powder, characterized in that: The following steps are involved: S1. Add a 1g-10g / L sodium chloroplatinate aqueous solution to a 1%-5% hydrazine hydrate solution at room temperature, stir thoroughly, and adjust the pH value of the reaction system to 5-10 in real time; The pH value of the reaction system is adjusted by using a sodium hydroxide aqueous solution or a hydrochloric acid aqueous solution with a mass concentration of 1%-2%, and the error range of the pH value is ±0.1; S2. After the addition of the sodium chloroplatinate aqueous solution is completed, the solution is stirred for 20 min-30 min, and the pH value of the reaction system is maintained at 5-10 to obtain platinum powder; S3. The obtained platinum powder is repeatedly washed and precipitated with deionized water to remove salt until the pH of the reaction system is neutral, and then washed with anhydrous ethanol to remove water; S4. After desalting and removing water, the platinum powder is vacuum dried to obtain micron-grade platinum powder with good uniformity, narrow particle size distribution, and D90-D10 < 3.1 μm.

2. The preparation method according to claim 1, characterized in that: The dropping rate of the sodium chloroplatinate aqueous solution in step S1 is 1.0 ml / min-10.0 ml / min.

3. The preparation method according to claim 1, characterized in that: The volume ratio of the sodium chloroplatinate aqueous solution to the hydrazine hydrate aqueous solution in step S1 is 1:0.2-2.

4. The preparation method according to claim 1, characterized in that: The stirring in step S1 is performed using an electric stirrer with a stirring speed of 100 r / min-500 r / min.

5. The preparation method according to claim 1, characterized in that: The method for judging the desalination in step S3 is as follows: take the supernatant after repeated washing and precipitation with deionized water, measure the pH value to be 6.5-7.5, add 2-3 drops of silver nitrate to the supernatant, and observe that no white precipitate is present, which means that the soluble salt has been removed.

6. The preparation method according to claim 1, characterized in that: The vacuum drying conditions in step S4 are as follows: temperature 60°C - 90°C, vacuum degree 0.08MPa, and drying time 12h - 24h.

7. The preparation method according to claim 1, characterized in that: Sodium chloroplatinate is the precursor and hydrazine hydrate is the reducing agent.

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