Method for preparing high-purity hafnium tetrachloride by wet extraction separation

Abstract

The application provides a method for preparing high-purity hafnium tetrachloride by wet extraction separation, and steps include: taking hafnium alloy waste as raw material, stirring and leaching by using HNO3 and HF mixed acid, then adding thioacetamide, adjusting pH to 4-5, and filtering after stirring; a composite extraction agent is obtained by compounding tributyl phosphate, trioctylphosphine oxide and sulfonated kerosene, and a homogeneous organic phase is formed by stirring and mixing; in a hydrochloric acid medium, the volume ratio of the organic phase to the aqueous phase is controlled to be 2.5-3.5:1, three-stage countercurrent extraction is carried out, and phase separation is carried out after standing; the organic phase after extraction passes through an adsorption column filled with imino-diacetic acid modified silica gel; hydrochloric acid solution is used for back extraction, then vacuum evaporation concentration is carried out, and hafnium tetrachloride is obtained after cooling crystallization and dehydration. In the application, the hafnium-zirconium separation efficiency in the hafnium tetrachloride preparation process is improved, and the problem of too high zirconium and hafnium impurity content in the product is solved.

Description

Technical Field

[0001] This invention relates to the field of separation and purification technology, specifically to a method for preparing high-purity hafnium tetrachloride by wet extraction and separation. Background Technology

[0002] In the field of rare metal hydrometallurgy, hafnium tetrachloride (HTC) plays a crucial role as a key compound. Its applications are wide-ranging, particularly in pharmaceuticals, fine organic synthesis, and the manufacture of semiconductor precursor materials, where it plays an irreplaceable role. In the semiconductor industry, high-purity HTC is an essential raw material for preparing semiconductor precursor materials. These precursor materials are used to grow high-quality thin films, which have a vital impact on the performance and stability of semiconductor devices. With the rapid development of semiconductor technology, the requirements for the quality and purity of high-purity electronic materials for semiconductors are becoming increasingly stringent. The purity and quality of HTC directly determine the growth quality and electrical properties of semiconductor thin films, thus affecting the performance and reliability of the entire semiconductor device.

[0003] Traditional methods for preparing hafnium tetrachloride primarily employ the chlorination roasting method. While this method can achieve hafnium tetrachloride production to a certain extent, it has several drawbacks. First, the chlorination roasting method is extremely energy-intensive, requiring a large amount of energy during production, which increases production costs. Second, this method generates severe chlorine pollution. Chlorine is a toxic and harmful gas, requiring significant investment in waste gas treatment during production, further increasing the production burden on enterprises. Furthermore, the chlorination roasting method is inefficient in separating zirconium and hafnium, resulting in a high content of zirconium and hafnium impurities in the product, making it difficult to meet the stringent purity requirements of high-purity hafnium tetrachloride for semiconductor electronic materials.

[0004] To overcome the shortcomings of the chlorination roasting method, some wet processes have attempted to directly separate zirconium and hafnium using a hydrochloric acid system. However, due to the extremely similar chemical properties of zirconium and hafnium, efficient separation in a hydrochloric acid system is difficult to achieve. Conventional extractants have poor selectivity for zirconium and hafnium, failing to effectively distinguish between them during extraction, necessitating multiple extraction cycles to achieve a certain separation effect. Multiple extraction cycles not only increase production time and cost but also easily introduce new impurities during the cycle, further affecting product purity. Therefore, existing hydrochloric acid-based wet processes also have significant limitations in the preparation of high-purity hafnium tetrachloride.

[0005] Currently, research on the preparation of hafnium tetrachloride from zirconium sulfate is relatively limited, and an efficient and environmentally friendly separation method is lacking. In practical production, how to efficiently separate zirconium and hafnium from zirconium sulfate and prepare high-purity hafnium tetrachloride remains an urgent problem to be solved.

[0006] Existing preparation methods suffer from numerous problems, making it difficult to meet the large market demand for high-purity hafnium tetrachloride. Therefore, this invention provides a wet extraction and separation method for preparing high-purity hafnium tetrachloride. Summary of the Invention

[0007] The purpose of this invention is to provide a method for preparing high-purity hafnium tetrachloride by wet extraction and separation, which improves the separation efficiency of zirconium and hafnium during the preparation of hafnium tetrachloride and solves the problem of excessive zirconium and hafnium impurity content in the product, so as to meet the strict requirements of high-purity electronic materials for semiconductor hafnium tetrachloride purity.

[0008] This invention provides a method for preparing high-purity hafnium tetrachloride by wet extraction and separation, comprising the following steps:

[0009] (1) Raw material pretreatment and acid leaching: Hafnium alloy waste was used as raw material. It was leached by stirring with a mixture of HNO3 and HF. Then, thioacetamide was added to adjust the pH to 4-5. After stirring, it was filtered.

[0010] (2) Preparation of the extractant system: Tributyl phosphate, trioctylphosphine oxide and sulfonated kerosene are compounded to obtain a composite extractant, which is then stirred and mixed to form a homogeneous organic phase;

[0011] (3) Extraction: In hydrochloric acid medium, the volume ratio of organic phase to aqueous phase is controlled at 2.5-3.5:1, and three-stage countercurrent extraction is carried out, followed by standing and phase separation;

[0012] (4) Dynamic adsorption: The extracted organic phase is passed through an adsorption column filled with iminodiacetic acid-modified silica gel;

[0013] (5) Back-extraction: Back-extraction is carried out using hydrochloric acid solution, followed by vacuum evaporation and concentration, cooling crystallization, and dehydration to obtain hafnium tetrachloride.

[0014] Furthermore, the ratio of the hafnium alloy waste, mixed acid, and thioacetamide is 8-12g: 45-55mL: 2-2.6g.

[0015] Furthermore, the volume ratio of HNO3 to HF in the mixed acid is 2:1.

[0016] Furthermore, the volume ratio of the tributyl phosphate, trioctylphosphine oxide, and sulfonated kerosene is 4-5:2-3:6-7.

[0017] Further, in step (3), the concentration of hydrochloric acid is 3-4 mol / L, the extraction temperature is 35-45℃, the mixing time for each stage of the three-stage countercurrent extraction is 15-25 min, and the settling and phase separation time is 10 min.

[0018] Further, the preparation method of the iminodiacetic acid modified silica gel includes: dissolving iminodiacetic acid in a mixture of ethanol and water, adding 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride and N-hydroxysuccinimide to obtain a mixture, impregnating amino-functionalized silica gel in the above mixture, and separating the silica gel after the reaction is completed to obtain modified silica gel.

[0019] Further, the ratio of the mixture of iminodiacetic acid, ethanol and water, 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride, N-hydroxysuccinimide and amino-functionalized silica gel is (2-3) g : (140-160) mL : (0.9-1) g : (0.55-0.65) g : (4.5-5.5) g.

[0020] Furthermore, the preparation method of the amino-functionalized silica gel includes: drying and dispersing nano-silica in toluene, adding 3-aminopropyltriethoxysilane, refluxing at 250-350 rpm and 70-80℃ for 5-6 hours under nitrogen protection, and then centrifuging, washing, and drying to obtain the product.

[0021] Furthermore, in step (5), the concentration of the hydrochloric acid solution is 3-4 mol / L, the back-extraction temperature is 35-45℃, and the back-extraction time is 30-40 min.

[0022] Furthermore, the dehydration temperature is 115-125℃, the vacuum degree is ≤-0.1 MPa, and the dehydration time is 2-3h.

[0023] The beneficial effects of this invention are as follows:

[0024] This invention employs a composite extractant formed by combining tributyl phosphate (TBP), trioctylphosphine oxide (Cyanex 923), and sulfonated kerosene. This combination overcomes the limitations of traditional single extractants. Cyanex 923 serves as the core extractant, and its phosphine oxide group in its molecular structure interacts with Zr... 4+ It exhibits unique high selectivity. From the perspective of coordination chemistry, the oxygen atom in the phosphine oxide group has a strong electron-donating ability and can react with Zr. 4+ Forming stable coordinate bonds, while for Hf 4+ Zr has relatively weak coordination ability. This makes Zr more susceptible to interference during extraction. 4+ It is easier to extract into the organic phase, thus effectively reducing Hf. 4+ The presence of organic phase residues improves the extraction purity of hafnium.

[0025] In this invention, the combination of TBP and Cyanex 923 is not a simple mixture, but rather produces a significant synergistic effect. During extraction, TBP can regulate the interfacial properties of the extraction system, improving the interfacial tension between the organic and aqueous phases. According to interfacial chemistry theory, suitable interfacial tension helps form a stable phase interface, avoiding emulsification. Simultaneously, TBP can also form mixed micelles with Cyanex 923, increasing the dispersibility and stability of the extractant in the organic phase, further improving extraction efficiency and phase separation stability. This synergistic effect results in higher selectivity and extraction efficiency for the composite extractant in hafnium-zirconium separation.

[0026] This invention utilizes iminodiacetic acid-modified silica gel as a dynamic adsorbent. The preparation process involves a chemical reaction between iminodiacetic acid and amino-functionalized silica gel, resulting in the grafting of iminodiacetic acid groups (IDA groups) onto the silica gel surface. The IDA molecule contains two carboxyl groups and one amino group; these functional groups can interact with Zr... 4+ Ti 4+ Impurity ions form stable chelates. From the perspective of chelation chemistry, carboxyl and amino groups can form five- or six-membered ring chelate structures with metal ions. These structures have high stability and can effectively fix impurity ions onto the adsorbent.

[0027] Compared to traditional dithizone and unmodified silica, IDA-modified silica exhibits better Zr activity. 4+ / Ti 4+ The chelation capacity is significantly improved. Although dithizone is also a chelating agent, its loading and stability on silica gel surfaces are poor, resulting in a low chelation capacity. Unmodified silica gel surfaces lack effective chelating functional groups, resulting in weak adsorption capacity for impurity ions. In contrast, IDA-modified silica gel, through chemical grafting, allows IDA groups to be uniformly distributed on the silica gel surface, greatly increasing the number and activity of chelation sites, thereby achieving the adsorption of Zr. 4+ / Ti 4+ Highly efficient deep impurity removal. Experimental results show that the chelating capacity of IDA-modified silica gel is much higher than that of dithizone and unmodified silica gel.

[0028] This invention uses thioacetamide to precipitate Fe. 3+ / Al 3+ The principle is that thioacetamide hydrolyzes in solution to produce H2S, and H2S reacts with Fe... 3+ / Al 3+ The reaction produces a sparingly soluble sulfide precipitate. Compared to the traditional H₂O₂ oxidation method, the thioacetamide precipitation method exhibits higher stability. The H₂O₂ oxidation method may result in Fe²⁺ precipitate if the reaction conditions are not properly controlled. 3+ Incomplete precipitation, residual Fe 3 +This will interfere with the extraction of hafnium during subsequent extraction processes, affecting the purity of the product. In contrast, the thioacetamide precipitation method has mild reaction conditions, high precipitation efficiency, and can ensure the purity of Fe. 3+ / Al 3+ Complete precipitation avoids interference from subsequent extraction. Attached Figure Description

[0029] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0030] Figure 1 This is the gas chromatogram of the product prepared in Example 1;

[0031] Figure 2 This is the gas chromatogram of the product prepared in Example 2;

[0032] Figure 3 This is the gas chromatogram of the product prepared in Example 3;

[0033] Figure 4 This is the gas chromatogram of the product prepared in Comparative Example 1;

[0034] Figure 5 This is the gas chromatogram of the product prepared in Comparative Example 2;

[0035] Figure 6 This is the gas chromatogram of the product prepared in Comparative Example 3;

[0036] Figure 7 This is the gas chromatogram of the product prepared in Comparative Example 4;

[0037] Figure 8 This is the gas chromatogram of the product prepared in Comparative Example 5;

[0038] Figure 9 This is the gas chromatogram of the product prepared in Comparative Example 6. Detailed Implementation

[0039] The technical solution of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0040] It should be noted that the hafnium alloy waste used in this invention was provided by the Ningbo Research Institute of Dalian University of Technology. The hafnium alloy waste contains the following elements in parts by weight: hafnium (Hf) 25.00%, titanium (Ti) 45.07%, aluminum (Al) 2.09%, iron (Fe) 8.52%, zirconium (Zr) 14.47%, with the balance being other unavoidable impurities.

[0041] The raw material in this invention is nano-silica with an average particle size of 70 nm and a specific surface area of ​​400 m². 2 / g; sulfonated kerosene, purchased from Jiangsu Wuyang Hydrogen Technology Co., Ltd.

[0042] Example 1

[0043] This embodiment provides a method for preparing high-purity hafnium tetrachloride by wet extraction and separation, the steps of which include:

[0044] (1) Raw material pretreatment and acid leaching: Hafnium alloy waste was used as raw material, with a hafnium content of 25%. It was ball-milled to 300 mesh and leached with a mixed acid of HNO3 and HF at a volume ratio of 2:1 at 80°C for 2 hours to obtain Hf-containing alloy. 4+ Zr 4+ Fe 3 + Ti 4+ An acidic solution was treated with 0.5 mol / L thioacetamide to selectively precipitate Fe. 3+ Al 3+ Adjust the pH to 4.5, stir at 200 rpm for 1 hour, and then filter. The ratio of hafnium alloy waste, mixed acid, and thioacetamide is 10 g: 50 mL: 2.3 g.

[0045] (2) Preparation of the extractant system:

[0046] A composite extractant was prepared by compounding 45 mL of tributyl phosphate, 25 mL of Lyanex 923 (trioctylphosphine oxide) and 65 mL of sulfonated kerosene. The mixture was stirred at room temperature and 600 rpm for 30 min to form a homogeneous organic phase.

[0047] (3) Extraction: In 4 mol / L hydrochloric acid medium, the volume ratio of organic phase to water phase is 3:1, and three-stage countercurrent extraction is performed. The temperature is controlled at 40℃, the mixing time for each stage is 20 min, and the settling time for phase separation is 10 min.

[0048] (4) Dynamic adsorption: The extracted organic phase was passed through an adsorption column packed with modified silica gel. The column height was 1.5 m, the flow rate was 2 BV / h, and the Zr content was... 4+ Ti 4+ Chelating and adsorption;

[0049] The preparation methods for modified silicone include:

[0050] 100 g of nano-silica was placed in a vacuum drying oven and dried at 120 °C for 2 h to remove surface adsorbed water. Then it was dispersed in 500 mL of toluene and ultrasonically dispersed for 30 min until uniform suspension was obtained. 10 mL of 3-aminopropyltriethoxysilane was added, and the mixture was refluxed at 300 rpm and 80 °C for 6 h under nitrogen protection. After the reaction was completed, the mixture was centrifuged at 5000 rpm for 10 min, the supernatant was discarded, and the mixture was washed three times with 200 mL of anhydrous ethanol each time to remove unreacted 3-aminopropyltriethoxysilane and toluene. The product was dried in a vacuum drying oven at 60 °C for 12 h to obtain amino-functionalized silica gel.

[0051] Weigh 2.45 g of iminodiacetic acid and dissolve it in 150 mL of a mixture of ethanol and water (ethanol to water volume ratio 4:1). Add 0.95 g of 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride and 0.58 g of N-hydroxysuccinimide to obtain a mixture. Impregnate 5 g of amino-functionalized silica gel in the above mixture and react for 12 h at 200 rpm and 50 °C under nitrogen protection. After the reaction is completed, filter to separate the silica gel and wash it three times each with 50 mL of ethanol and deionized water. Dry it under vacuum at 40 °C for 6 h to obtain modified silica gel.

[0052] (5) Back-extraction: Back-extraction was performed using 3.5 mol / L hydrochloric acid aqueous solution at a temperature of 40℃ for 30 min. The back-extraction solution was concentrated to 1 / 5 of its original volume by vacuum evaporation at -0.08 MPa at 60℃. After cooling and crystallization, HfCl4·6H2O crystals were obtained.

[0053] (6) Vacuum dehydration: The crystal was dehydrated at 120℃ and vacuum degree -0.1 MPa for 2h to obtain anhydrous HfCl4.

[0054] Figure 1 The gas chromatogram data are shown in the table below:

[0055]

[0056] Example 2

[0057] This embodiment provides a method for preparing high-purity hafnium tetrachloride by wet extraction and separation, the steps of which include:

[0058] (1) Raw material pretreatment and acid leaching: Hafnium alloy waste was used as raw material, with a hafnium content of 25%. The waste was ball-milled to 300 mesh and leached with a mixed acid of HNO3 and HF at a volume ratio of 2:1 at 75°C for 1.5 h with stirring to obtain a hafnium-containing alloy. 4+ Zr 4+ Fe 3+ Ti4+ An acidic solution was treated with 0.5 mol / L thioacetamide to selectively precipitate Fe. 3+ Al 3+ Adjust the pH to 4, stir at 200 rpm for 1 hour, and then filter. The ratio of hafnium alloy waste, mixed acid and thioacetamide is 8g:45mL:2g.

[0059] (2) Preparation of the extractant system:

[0060] A composite extractant was prepared by compounding 40 mL of tributyl phosphate, 20 mL of Cyanex 923 (trioctylphosphine oxide) and 60 mL of sulfonated kerosene. The mixture was stirred at room temperature and 600 rpm for 30 min to form a homogeneous organic phase.

[0061] (3) Extraction: In 3 mol / L hydrochloric acid medium, the volume ratio of organic phase to aqueous phase is 2.5:1, three-stage countercurrent extraction is performed, the temperature is controlled at 35℃, the mixing time of each stage is 15 min, and the settling time for phase separation is 8 min;

[0062] (4) Dynamic adsorption: The extracted organic phase was passed through an adsorption column packed with modified silica gel. The column height was 1.5 m, the flow rate was 2 BV / h, and the Zr content was... 4+ Ti 4+ Chelating and adsorption;

[0063] The preparation methods for modified silicone include:

[0064] 100 g of nano-silica was placed in a vacuum drying oven and dried at 120 °C for 2 h to remove surface adsorbed water. Then it was dispersed in 500 mL of toluene and ultrasonically dispersed for 30 min until uniform suspension was obtained. 10 mL of 3-aminopropyltriethoxysilane was added, and the mixture was refluxed at 250 rpm and 70 °C for 5 h under nitrogen protection. After the reaction was completed, the mixture was centrifuged at 5000 rpm for 10 min, the supernatant was discarded, and the product was washed three times with 200 mL of anhydrous ethanol each time to remove unreacted 3-aminopropyltriethoxysilane and toluene. The product was dried in a vacuum drying oven at 60 °C for 12 h to obtain amino-functionalized silica gel.

[0065] Weigh 2g of iminodiacetic acid and dissolve it in 140mL of a mixture of ethanol and water (ethanol to water volume ratio 4:1). Add 0.9g of 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride and 0.55g of N-hydroxysuccinimide to obtain a mixture. Impregnate 4.5g of aminofunctionalized silica gel in the above mixture and react for 12h under nitrogen protection at 200 rpm and 50℃. After the reaction is completed, filter to separate the silica gel, wash it three times each with 50 mL of ethanol and deionized water, and dry it under vacuum at 40℃ for 6h to obtain modified silica gel.

[0066] (5) Back-extraction: Back-extraction was carried out using 3 mol / L hydrochloric acid aqueous solution at 35℃ for 30 min. The back-extraction solution was concentrated to 1 / 5 of its original volume by vacuum evaporation at -0.08 MPa at 60℃. After cooling and crystallization, HfCl4·6H2O crystals were obtained.

[0067] (6) Vacuum dehydration: The crystal was dehydrated at 115℃ and vacuum degree -0.1 MPa for 2h to obtain anhydrous HfCl4.

[0068] Figure 2 The gas chromatogram data are shown in the table below:

[0069]

[0070] Example 3

[0071] This embodiment provides a method for preparing high-purity hafnium tetrachloride by wet extraction and separation, the steps of which include:

[0072] (1) Raw material pretreatment and acid leaching: Hafnium alloy waste was used as raw material, with a hafnium content of 25%. The waste was ball-milled to 300 mesh and leached with a mixed acid of HNO3 and HF at a volume ratio of 2:1 at 85°C for 2.5 h with stirring to obtain Hf-containing waste. 4+ Zr 4+ Fe 3+ Ti 4+ An acidic solution was treated with 0.5 mol / L thioacetamide to selectively precipitate Fe. 3+ Al 3+ Adjust the pH to 5, stir at 200 rpm for 1 hour, and then filter. The ratio of hafnium alloy waste, mixed acid and thioacetamide is 12g:55mL:2.6g.

[0073] (2) Preparation of the extractant system:

[0074] A composite extractant was prepared by compounding 50 mL of tributyl phosphate, 30 mL of Lyanex 923 (trioctylphosphine oxide) and 70 mL of sulfonated kerosene. The mixture was stirred at room temperature and 600 rpm for 30 min to form a homogeneous organic phase.

[0075] (3) Extraction: In 3 mol / L hydrochloric acid medium, the volume ratio of organic phase to aqueous phase is 3.5:1, three-stage countercurrent extraction is performed, the temperature is controlled at 45℃, the mixing time of each stage is 25 min, and the settling time for phase separation is 12 min;

[0076] (4) Dynamic adsorption: The extracted organic phase was passed through an adsorption column packed with modified silica gel. The column height was 1.5 m, the flow rate was 2 BV / h, and the Zr content was... 4+ Ti 4+ Chelating and adsorption;

[0077] The preparation methods for modified silicone include:

[0078] 100 g of nano-silica was placed in a vacuum drying oven and dried at 120 °C for 2 h to remove surface adsorbed water. Then it was dispersed in 500 mL of toluene and ultrasonically dispersed for 30 min until uniform suspension was obtained. 10 mL of 3-aminopropyltriethoxysilane was added, and the mixture was refluxed at 350 rpm and 80 °C for 6 h under nitrogen protection. After the reaction was completed, the mixture was centrifuged at 5000 rpm for 10 min, the supernatant was discarded, and the mixture was washed three times with 200 mL of anhydrous ethanol each time to remove unreacted 3-aminopropyltriethoxysilane and toluene. The product was dried in a vacuum drying oven at 60 °C for 12 h to obtain amino-functionalized silica gel.

[0079] Weigh 3g of iminodiacetic acid and dissolve it in 160mL of a mixture of ethanol and water (ethanol to water volume ratio 4:1). Add 1g of 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride and 0.65g of N-hydroxysuccinimide to obtain a mixture. Impregnate 5.5g of aminofunctionalized silica gel in the above mixture and react for 12 h at 200 rpm and 50℃ under nitrogen protection. After the reaction is completed, filter to separate the silica gel, wash it three times each with 50 mL of ethanol and deionized water, and dry it under vacuum at 40℃ for 6 h to obtain modified silica gel.

[0080] (5) Back-extraction: Back-extraction was carried out using 4 mol / L hydrochloric acid aqueous solution at 45℃ for 40 min. The back-extraction solution was concentrated to 1 / 5 of its original volume by vacuum evaporation at -0.08 MPa at 60℃. After cooling and crystallization, HfCl4·6H2O crystals were obtained.

[0081] (6) Vacuum dehydration: The crystal was dehydrated at 125℃ and vacuum degree -0.1 MPa for 3h to obtain anhydrous HfCl4.

[0082] Figure 3 The gas chromatogram data are shown in the table below:

[0083]

[0084] Comparative Example 1

[0085] In Comparative Example 1, thioacetamide was replaced with 5 mL of 30% H2O2 aqueous solution, the pH was adjusted to 5.0, and the mixture was stirred for 1 h. The rest of the process was the same as in Example 1, and the preparation steps were the same as in Example 1.

[0086] Figure 4 The gas chromatogram data are shown in the table below:

[0087]

[0088] Comparative Example 2

[0089] In Comparative Example 2, Cyanex 923 was replaced with di(2-ethylhexyl) phosphate (P507), and the rest was the same as in Example 1, with the same preparation steps.

[0090] Figure 5 The gas chromatogram data are shown in the table below:

[0091]

[0092] Comparative Example 3

[0093] The extractant system in Comparative Example 3 did not include Cyanex 923, but was otherwise the same as in Example 1, and the preparation steps were the same as in Example 1.

[0094] Figure 6 The gas chromatogram data are shown in the table below:

[0095]

[0096] Comparative Example 4

[0097] The modified silica gel in Comparative Example 4 was a dithizone-modified silica gel. The preparation steps included: weighing 1.96 g of dithizone and dissolving it in 500 mL of anhydrous ethanol, ultrasonically dispersing it for 20 minutes, immersing 50 g of amino-functionalized silica gel in the above solution, magnetically stirring it for 12 hours under light-protected conditions, filtering to separate the silica gel, rinsing it three times with a small amount of ethanol, and vacuum drying it at 40°C for 6 hours to obtain the silica gel. The rest was the same as in Example 1, and the preparation steps were the same as in Example 1.

[0098] Figure 7 The gas chromatogram data are shown in the table below:

[0099]

[0100] Comparative Example 5

[0101] In Comparative Example 5, the modified silica gel was an amino-functionalized silica gel that was not further modified with iminodiacetic acid. The pH was adjusted to 5.0, and the mixture was stirred for 1 h. The rest of the process was the same as in Example 1, and the preparation steps were the same as in Example 1.

[0102] Figure 8 The gas chromatogram data are shown in the table below:

[0103]

[0104] Comparative Example 6

[0105] In Comparative Example 6, the organic phase after extraction was directly introduced into the back-extraction column without passing through the modified silica adsorption column. The rest was the same as in Example 1, and the preparation steps were the same as in Example 1.

[0106] Figure 9 The gas chromatogram data are shown in the table below:

[0107]

[0108] Experimental example: A comparison was made between the wet extraction separation methods for preparing high-purity hafnium tetrachloride in Examples 1-3 and Comparative Examples 1-6:

[0109] HfCl4 purity: Tested according to GB / T 9722-2023 "General Rules for Gas Chromatography of Chemical Reagents":

[0110] The method for detecting Zr, a metallic impurity in hafnium tetrachloride, is as follows: The determination is performed using an inductively coupled plasma atomic emission spectrometer (Thermo Fisher Scientific, iCAP PRO).

[0111] Process stability: The purity of HfCl4 was repeatedly tested 10 times. High stability: small fluctuations in results, good reproducibility, RSD <1%; Medium stability: some fluctuations in results, but acceptable or within a controllable range, RSD 1%-3%; Low / extremely low process stability: large fluctuations in results, poor reproducibility, difficulty in consistently producing qualified products, RSD >3% or higher.

[0112] Table 1

[0113]

[0114] Based on the above data, it can be concluded that Cyanex 923 is the core component for hafnium-zirconium separation: its phosphine oxide group is crucial for Zr... 4+ Its high selectivity is significantly better than P507 (phosphate esters), and it can reduce Hf. 4+ Residue in the organic phase. The combination of TBP and Cyanex 923 can improve phase separation stability and avoid emulsification. IDA-modified silica gel for Zr... 4+ / Ti 4+ The chelation capacity of the chelate exceeds that of dithizone and unmodified silica gel, thus ensuring deep impurity removal; however, omitting the adsorption step leads to excessive Zr content, proving that dynamic adsorption is indispensable for improving purity. Furthermore, thioacetamide precipitates Fe. 3+ / Al 3+ Its stability is better than that of the H2O2 oxidation method, the latter may be due to Fe 3+ Incomplete precipitation leads to interference with subsequent extraction.

[0115] In this invention, the dynamic adsorption step plays a crucial role in the entire process. Omitting the adsorption step leads to excessive Zr content in the product; as shown in Comparative Example 6, the Zr content is as high as 0.15%. This is because although most of the Zr is extracted during the process... 4+ It is extracted into the organic phase, but a small amount of Zr will still remain. 4+These Zr residues remain in the aqueous phase. A dynamic adsorption step can further remove these residual Zr. 4+ This ensures the purity of the final product. Dynamic adsorption of IDA-modified silica gel reduces impurity levels in the product to extremely low levels, meeting the requirements for preparing high-purity hafnium tetrachloride.

[0116] Finally, it should be noted that the above embodiments are only used to illustrate the present invention and are not intended to limit the technical solutions described in the present invention; those skilled in the art should understand that modifications or equivalent substitutions can still be made to the present invention; and all technical solutions and improvements that do not depart from the spirit and scope of the present invention should be covered within the scope of the claims of the present invention.

Claims

1. A method for producing high purity hafnium tetrachloride by wet extraction separation, characterized by, The steps include; (1) Raw material pretreatment and acid leaching: Hafnium alloy waste was used as raw material. It was leached by stirring with a mixture of HNO3 and HF. Then, thioacetamide was added to adjust the pH to 4-5. After stirring, it was filtered. (2) Preparation of the extractant system: Tributyl phosphate, trioctylphosphine oxide and sulfonated kerosene are compounded to obtain a composite extractant, which is then stirred and mixed to form a homogeneous organic phase; (3) Extraction: In hydrochloric acid medium, the volume ratio of organic phase to aqueous phase is controlled at 2.5-3.5:1, and three-stage countercurrent extraction is carried out, followed by standing and phase separation; (4) Dynamic adsorption: The extracted organic phase is passed through an adsorption column filled with iminodiacetic acid-modified silica gel; (5) Back-extraction: Back-extraction is carried out using hydrochloric acid solution, followed by vacuum evaporation and concentration, cooling crystallization, and dehydration to obtain hafnium tetrachloride.

2. The method for preparing high-purity hafnium tetrachloride by wet extraction separation according to claim 1, characterized in that, The ratio of hafnium alloy waste, mixed acid, and thioacetamide is 8-12g: 45-55mL: 2-2.6g.

3. The method of claim 1, wherein the method is characterized by, The stirring and leaching time is 1.5-2.5 hours, and the temperature is 75-85℃.

4. The method of claim 1, wherein the method is a method of preparing high purity hafnium tetrachloride by wet extraction separation, characterized by, The volume ratio of tributyl phosphate, trioctylphosphine oxide, and sulfonated kerosene is 4-5:2-3:6-7.

5. The method of claim 1, wherein the method is a method of preparing high purity hafnium tetrachloride by wet extraction separation, characterized by, In step (3), the concentration of hydrochloric acid is 3-4 mol / L, the extraction temperature is 35-45℃, the mixing time for each stage of the three-stage countercurrent extraction is 15-25 min, and the settling and phase separation time is 8-12 min.

6. The method of claim 1, wherein the method is a method of preparing high purity hafnium tetrachloride by wet extraction separation, characterized by, The preparation method of the iminodiacetic acid modified silica gel includes: dissolving iminodiacetic acid in a mixture of ethanol and water, adding 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride and N-hydroxysuccinimide to obtain a mixture, impregnating amino-functionalized silica gel in the above mixture, and separating the silica gel after the reaction is completed to obtain modified silica gel.

7. The method of claim 6, wherein the method is a method of producing high purity hafnium tetrachloride by wet extraction separation, characterized by, The ratio of the mixture of iminodiacetic acid, ethanol and water, 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride, N-hydroxysuccinimide and amino-functionalized silica gel is (2-3) g : (140-160) mL : (0.9-1) g : (0.55-0.65) g : (4.5-5.5) g.

8. The method of claim 6, wherein the method is a method of preparing high purity hafnium tetrachloride by wet extraction separation, characterized in that, The preparation method of the amino-functionalized silica gel includes: drying and dispersing nano-silica in toluene, adding 3-aminopropyltriethoxysilane, refluxing at 250-350 rpm and 70-80℃ for 5-6 hours under nitrogen protection, and then centrifuging, washing and drying to obtain the product.

9. The method of claim 1, wherein the method is a method of preparing high purity hafnium tetrachloride by wet extraction separation, characterized by, In step (5), the concentration of hydrochloric acid solution is 3-4 mol / L, the back-extraction temperature is 35-45℃, and the back-extraction time is 30-40 min.

10. The method of claim 1, wherein the method is a method of preparing high purity hafnium tetrachloride by wet extraction separation, characterized by, The dehydration temperature is 115-125℃, the vacuum degree is ≤-0.1 MPa, and the dehydration time is 2-3h.

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