Preparation method of high-purity metal hafnium

Abstract

This invention relates to the field of rare metals technology and proposes a method for preparing high-purity metallic hafnium. The method involves dissolving hafnium-containing waste, followed by extraction, washing, back-extraction, precipitation, and calcination to obtain high-purity metallic hafnium. The organic phase reagent used in the extraction comprises the following components by weight: 20-30 parts tributyl phosphate, 6-8 parts synergist, and 200-300 parts diluent. The synergist includes one or two of dodecyl phosphate, hexadecyl phosphate, and octadecyl phosphate. This technical solution solves the problem of low purity of metallic hafnium in related technologies.

Description

Technical Field

[0001] This invention relates to the field of rare metals technology, specifically to a method for preparing high-purity hafnium metal. Background Technology

[0002] Due to its unique physicochemical properties, metallic hafnium is widely used in various fields such as nuclear industry, electronics and semiconductor industry, and aerospace. Producing metallic hafnium from hafnium-containing waste can reduce production costs and environmental pollution. However, because hafnium and zirconium are closely associated in minerals such as zircon in nature, hafnium-containing waste also contains zirconium. Since hafnium and zirconium are difficult to separate easily, zirconium impurities will be present in metallic hafnium, leading to a decrease in its purity.

[0003] Currently, extraction processes are commonly used to further improve the purity of metallic hafnium. Extraction systems for metallic hafnium include tributyl phosphate-nitric acid extraction and thiocyanate-isohexanone extraction. Compared to the thiocyanate-isohexanone extraction system, the tributyl phosphate-nitric acid extraction system is more mature and can be used for continuous production. However, tributyl phosphate has a relatively small difference in its extraction capacity for zirconium and hafnium, and zirconium can interfere with the extraction and separation of hafnium, leading to a decrease in the purity of metallic hafnium. Summary of the Invention

[0004] This invention proposes a method for preparing high-purity metallic hafnium, which solves the problem of low purity of metallic hafnium in related technologies.

[0005] The technical solution of the present invention is as follows:

[0006] This invention proposes a method for preparing high-purity metallic hafnium, comprising the following steps: dissolving hafnium-containing waste, followed by extraction, washing, back-extraction, precipitation, and calcination to obtain high-purity metallic hafnium. The organic phase reagent used in the extraction comprises the following components by weight: 20-30 parts tributyl phosphate, 6-8 parts synergist, and 200-300 parts diluent. The synergist comprises one or two of dodecyl phosphate, hexadecyl phosphate, and octadecyl phosphate.

[0007] As a further technical solution, the synergist is composed of dodecyl phosphate and octadecyl phosphate.

[0008] As a further technical solution, the mass ratio of dodecyl phosphate to octadecyl phosphate is 1 to 3:1, for example, it can be 1:1, 1.5:1, 2:1, 2.5:1, 3:1, preferably 1:1.

[0009] In this invention, the synergist in the organic phase reagent used for extraction is limited to dodecyl phosphate and octadecyl phosphate, and their ratio is limited to 1~3:1. The reason for this is that the synergist contains a long alkyl carbon chain with an electron-donating group, which can improve the extraction ability of the extractant and the separation degree of zirconium and hafnium. However, if the alkyl carbon chain is too long, there will be a steric hindrance effect, which will reduce the extraction ability. In the organic phase reagent system of this invention, limiting the synergist in the organic phase reagent to dodecyl phosphate and octadecyl phosphate, and limiting their ratio to 1~3:1, can better improve the extraction ability of the extractant, the separation degree of zirconium and hafnium, and improve the purity of metallic hafnium.

[0010] As a further technical solution, the hafnium-containing waste is derived from high-temperature alloy waste.

[0011] Because the processing flow of hafnium-containing high-temperature alloy products is long and the yield is low, a large amount of high-temperature alloy waste is generated in the process of high-temperature alloy production. In addition to hafnium and zirconium, high-temperature alloy waste also contains metal elements such as nickel, cobalt, tungsten, and titanium.

[0012] As a further technical solution, the diluent includes one of gasoline and sulfonated kerosene.

[0013] In this invention, the diluent used in the organic phase reagent for extraction includes either gasoline or sulfonated kerosene. Both gasoline and sulfonated kerosene are hydrocarbon mixtures and have good solubility for tributyl phosphate and synergists, which can form a stable extraction system. Furthermore, the polarity of the extractant can be adjusted to enhance the extraction rate of hafnium and reduce impurities in metallic hafnium.

[0014] As a further technical solution, the acid solution used to dissolve the hafnium-containing waste is a 30wt%~35wt% nitric acid aqueous solution.

[0015] As a further technical solution, a co-extractant is added during the extraction process, wherein the co-extractant is a compound containing hydroxyl and fluorine atoms.

[0016] In this invention, a compound containing hydroxyl and fluorine atoms is added as a co-extractant during the extraction process. The compound containing hydroxyl and fluorine atoms has hydroxyl and fluorine atoms, and their synergistic effect can form coordinate bonds with hafnium, increase the binding sites, improve the extraction rate of hafnium and the separation degree of hafnium and zirconium, and reduce the content of impurities in metallic hafnium.

[0017] As a further technical solution, the amount of the co-extractant added is 10% to 14% of the mass of tributyl phosphate, for example, it can be 10%, 12%, or 14%, preferably 12%.

[0018] Adding too much or too little of compounds containing hydroxyl and fluorine atoms can affect the extraction rate of hafnium and the content of impurities. The present invention limits the amount of co-extractant added, which can improve the extraction rate of hafnium and reduce the content of impurities in metallic hafnium.

[0019] As a further technical solution, the compound containing hydroxyl and fluorine atoms includes one or more of 2-fluoroethanol, 4-fluorophenol, 2,3-difluorophenol, and o-trifluoromethylphenol.

[0020] As a further technical solution, the compound containing hydroxyl and fluorine atoms is preferably 4-fluorophenol, 2,3-difluorophenol, or o-trifluoromethylphenol, and more preferably 2,3-difluorophenol.

[0021] In this invention, the co-extractant is preferably a compound containing hydroxyl and fluorine atoms, such as 4-fluorophenol, 2,3-difluorophenol, or o-trifluoromethylphenol, which can better form a stable coordination structure with hafnium ions. During extraction, it can further transfer hafnium ions from the aqueous phase to the organic phase, improve the extraction rate of hafnium and the separation degree between hafnium and zirconium, and reduce the impurities of metallic hafnium.

[0022] As a further technical solution, the volume ratio of the organic phase and the hafnium-containing waste solution during extraction is 1~2:1, for example, it can be 1:1, 1.2:1, 1.4:1, 1.6:1, 1.8:1, or 2:1.

[0023] As a further technical solution, the extraction temperature is 25~35℃, for example, 25℃, 30℃, or 35℃, and the extraction time is 30~40min, for example, 30min, 35min, or 40min.

[0024] As a further technical solution, the washing involves adding the extracted hafnium-containing organic phase to a detergent and mixing for 5-8 minutes, for example, 5 minutes, 6 minutes, 7 minutes, or 8 minutes, to obtain the washed hafnium-containing organic phase.

[0025] As a further technical solution, the volume ratio of the extracted hafnium-containing organic phase to the detergent is 2:1.

[0026] As a further technical solution, the detergent is a 4~6 mol / L nitric acid aqueous solution, for example, it can be 4 mol / L, 4.5 mol / L, 5 mol / L, 5.5 mol / L, or 6 mol / L.

[0027] As a further technical solution, the back-extraction involves adding the washed hafnium-containing organic phase to the back-extraction agent and mixing for 3-5 minutes to obtain a back-extraction solution, for example, for 3 minutes, 4 minutes, or 5 minutes.

[0028] As a further technical solution, the stripping agent is an 8-10 mol / L nitric acid aqueous solution, for example, it can be 8 mol / L, 8.5 mol / L, 9 mol / L, 9.5 mol / L, or 10 mol / L.

[0029] As a further technical solution, the volume ratio of the washed hafnium-containing organic phase to the stripping agent is 5:1.

[0030] As a further technical solution, the precipitation is achieved by mixing the back-extraction solution obtained after back-extraction with ammonia water to induce precipitation.

[0031] The working principle and beneficial effects of this invention are as follows:

[0032] The organic phase reagents used in the extraction process of this invention include tributyl phosphate, a synergist, and a diluent. The synergist includes one or two of dodecyl phosphate, hexadecyl phosphate, and octadecyl phosphate. The addition of the synergist significantly improves the extraction capacity of hafnium from hafnium-containing waste, thereby increasing the extraction rate and purity of metallic hafnium. In existing technologies, tributyl phosphate is used to extract metallic hafnium using a tributyl phosphate-nitric acid system, which utilizes the different extraction capacities of tributyl phosphate for zirconium and hafnium. However, the difference in extraction capacity of tributyl phosphate for zirconium and hafnium is relatively small, resulting in low purity of the final metallic hafnium. This invention adds a diluent to the tributyl phosphate-nitric acid system, and also adds one or two of dodecyl phosphate, hexadecyl phosphate, and octadecyl phosphate as synergists. Tributyl phosphate can form a complex by coordinating oxygen atoms with hafnium ions, while the synergists can make the structure of the complex more stable by introducing P=O and long alkyl carbon chains. Through the synergistic effect of tributyl phosphate and synergists, the extraction rate and purity of metallic hafnium can be improved. Furthermore, adding a diluent to the extraction organic phase composed of tributyl phosphate and synergists can change the polarity of the organic phase, reduce the interfacial tension of the organic phase, and improve the extraction efficiency and the purity of metallic hafnium. Detailed Implementation

[0033] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0034] Example 1

[0035] A method for preparing high-purity metallic hafnium includes the following steps:

[0036] S1. Add hafnium-containing waste to a 30wt% nitric acid aqueous solution to obtain a solution;

[0037] The mass-to-volume ratio of hafnium-containing waste to 30wt% nitric acid aqueous solution is 1g:2mL;

[0038] S2. Add the solution to the organic phase and extract at 25°C for 40 min to obtain the hafnium-containing organic phase. Mix with 4 mol / L nitric acid aqueous solution for 8 min, wash, and obtain the washed hafnium-containing organic phase.

[0039] The organic phase comprises the following components by weight: 20 parts tributyl phosphate, 6 parts dodecyl phosphate, and 200 parts diluent; the volume ratio of the organic phase to the solution is 1:1; the volume ratio of the hafnium-containing organic phase to the 4 mol / L nitric acid aqueous solution is 2:1; and the diluent is 260# sulfonated kerosene.

[0040] S3. After washing the hafnium-containing organic phase, mix it with an 8 mol / L nitric acid aqueous solution for 5 min and then back-extract to obtain a hafnium-containing solution; wherein the volume ratio of the washed hafnium-containing organic phase to the 8 mol / L nitric acid aqueous solution is 5:1.

[0041] S4. Mix the hafnium-containing solution with ammonia water, precipitate the hafnium, and then calcine it to obtain high-purity metallic hafnium.

[0042] Testing revealed that the total impurity content in the obtained high-purity hafnium metal was 16 ppm, with zirconium accounting for 24.31% of the total impurities, and the hafnium yield was 91.03%.

[0043] Example 2

[0044] A method for preparing high-purity metallic hafnium includes the following steps:

[0045] S1. Add hafnium-containing waste to a 35wt% nitric acid aqueous solution to obtain a solution;

[0046] The mass-to-volume ratio of hafnium-containing waste to 35wt% nitric acid aqueous solution is 1g:3mL;

[0047] S2. Add the solution to the organic phase and extract at 35°C for 30 min to obtain the hafnium-containing organic phase. Mix with 6 mol / L nitric acid aqueous solution for 5 min, wash, and obtain the washed hafnium-containing organic phase.

[0048] The organic phase comprises the following components by weight: 30 parts tributyl phosphate, 8 parts dodecyl phosphate, and 300 parts diluent; the volume ratio of the organic phase to the solution is 2:1; the volume ratio of the hafnium-containing organic phase to the 6 mol / L nitric acid aqueous solution is 2:1; and the diluent is 260# sulfonated kerosene.

[0049] S3. After washing the hafnium-containing organic phase, mix it with 10 mol / L nitric acid aqueous solution for 3 min and then back-extract to obtain a hafnium-containing solution; wherein the volume ratio of the washed hafnium-containing organic phase to the 10 mol / L nitric acid aqueous solution is 5:1.

[0050] S4. Mix the hafnium-containing solution with ammonia water, precipitate the hafnium, and then calcine it to obtain high-purity metallic hafnium.

[0051] Testing revealed that the total impurity content in the high-purity hafnium metal was 18 ppm, with zirconium accounting for 25.72% of the total impurities, and the hafnium yield was 90.52%.

[0052] Example 3

[0053] Compared with Example 1, the only difference in Example 3 is that dodecyl phosphate is replaced with an equal amount of octadecyl phosphate;

[0054] Testing revealed that the total impurity content in the obtained high-purity hafnium metal was 15 ppm, with zirconium accounting for 23.13% of the total impurities, and the hafnium yield was 91.27%.

[0055] Example 4

[0056] Compared with Example 1, the only difference in Example 4 is that dodecyl phosphate is replaced with equal amounts of dodecyl phosphate and octadecyl phosphate in a mass ratio of 1:1.

[0057] The test results showed that the total impurity content of the high-purity hafnium metal was 12 ppm, the zirconium content of the total impurities was 20.33%, and the hafnium yield was 94.89%.

[0058] Example 5

[0059] Compared with Example 1, the only difference in Example 5 is that dodecyl phosphate is replaced with equal amounts of dodecyl phosphate and hexadecyl phosphate in a mass ratio of 1:1.

[0060] The test results showed that the total impurity content of the high-purity hafnium metal was 14 ppm, the zirconium content of the total impurities was 19.0%, and the hafnium yield was 93.12%.

[0061] Example 6

[0062] Compared with Example 1, the only difference in Example 6 is that dodecyl phosphate is replaced with equal amounts of octadecyl phosphate and hexadecyl phosphate in a mass ratio of 1:1.

[0063] Testing revealed that the total impurity content in the obtained high-purity hafnium metal was 15 ppm, with zirconium accounting for 19.2% of the total impurities, and the hafnium yield was 92.65%.

[0064] Example 7

[0065] Compared with Example 5, the only difference in Example 7 is that 2-fluoroethanol was added to the solution in this example, and the amount of 2-fluoroethanol added was 12% of the mass of tributyl phosphate;

[0066] Testing revealed that the total impurity content in the obtained high-purity hafnium metal was 9 ppm, with zirconium accounting for 15.67% of the total impurities, and the hafnium yield was 95.22%.

[0067] Example 8

[0068] Compared with Example 5, the only difference in Example 8 is that 4-fluorophenol was added to the organic phase in this example, and the amount of 4-fluorophenol added was 12% of the mass of tributyl phosphate;

[0069] Testing revealed that the total impurity content in the high-purity hafnium metal was 7 ppm, with zirconium accounting for 12.29% of the total impurities, and the hafnium yield was 95.79%.

[0070] Example 9

[0071] The only difference between Example 9 and Example 8 is that 4-fluorophenol is replaced with an equal amount of 2,3-difluorophenol.

[0072] Testing revealed that the total impurity content in the obtained high-purity hafnium metal was 4 ppm, the zirconium content in the total impurities was 8.25%, and the hafnium yield was 96.83%.

[0073] Example 10

[0074] The only difference between Example 10 and Example 8 is that 4-fluorophenol is replaced with an equal amount of o-trifluoromethylphenol;

[0075] Testing revealed that the total impurity content in the high-purity hafnium metal was 5 ppm, with zirconium accounting for 10.2% of the total impurities, and the hafnium yield was 96.12%.

[0076] Comparative Example 1

[0077] Compared with Example 1, the only difference in this comparative example is that no dodecyl phosphate is added;

[0078] Testing revealed that the total impurity content in the obtained high-purity hafnium metal was 20 ppm, with zirconium accounting for 30.0% of the total impurities, and the hafnium yield was 87.61%.

[0079] By comparing Examples 1-10 with the Comparative Example, it can be seen that the extraction rate of hafnium and the purity of metallic hafnium in Examples 1-10 of the present invention are higher than those in Comparative Example 1, indicating that the addition of alkyl phosphate esters to the organic phase of the present invention can improve the extraction rate of hafnium and the purity of metallic hafnium.

[0080] By comparing Examples 1-6 with Examples 7-10, it can be seen that the extraction rate of hafnium and the purity of metallic hafnium in Examples 7-10 are higher than those in Examples 1-6, indicating that the addition of a co-extractant during the extraction process of the present invention can further improve the extraction rate of hafnium and the purity of metallic hafnium.

[0081] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing high-purity metallic hafnium, characterized in that, Includes the following steps: After dissolving hafnium-containing waste, high-purity metallic hafnium is obtained through extraction, washing, back-extraction, precipitation, and calcination. The organic phase reagent used in the extraction includes the following components by weight: 20-30 parts tributyl phosphate, 6-8 parts synergist, and 200-300 parts diluent. The synergist includes one or two of dodecyl phosphate, hexadecyl phosphate, and octadecyl phosphate.

2. The method for preparing high-purity metallic hafnium according to claim 1, characterized in that, The diluent includes either gasoline or sulfonated kerosene.

3. The method for preparing high-purity metallic hafnium according to claim 1, characterized in that, The acid solution used to dissolve the hafnium-containing waste is a 30wt%~35wt% nitric acid aqueous solution.

4. The method for preparing high-purity metallic hafnium according to claim 1, characterized in that, The extraction process also includes the addition of a co-extractant, which is a compound containing hydroxyl and fluorine atoms.

5. The method for preparing high-purity metallic hafnium according to claim 4, characterized in that, The compounds containing hydroxyl and fluorine atoms include one or more of 2-fluoroethanol, 4-fluorophenol, 2,3-difluorophenol, and o-trifluoromethylphenol.

6. The method for preparing high-purity metallic hafnium according to claim 1, characterized in that, The volume ratio of the organic phase to the hafnium-containing waste solution during extraction is 1~2:

1.

7. The method for preparing high-purity metallic hafnium according to claim 1, characterized in that, The extraction temperature is 25~35℃, and the extraction time is 30~40min.

8. The method for preparing high-purity metallic hafnium according to claim 1, characterized in that, The washing process involves mixing the extracted hafnium-containing organic phase with a detergent for 5-8 minutes to obtain a washed hafnium-containing organic phase.

9. The method for preparing high-purity metallic hafnium according to claim 8, characterized in that, The detergent is a 4-6 mol / L nitric acid aqueous solution.

10. The method for preparing high-purity metallic hafnium according to claim 1, characterized in that, The precipitation is achieved by mixing the back-extraction solution obtained after back-extraction with ammonia water.