Method for converting hafnium oxalate feed liquid into hafnium sulfate feed liquid

Abstract

The invention relates to the field of hydrometallurgy, and discloses a method for converting hafnium oxalate feed liquid into hafnium sulfate feed liquid, which comprises the following steps: adding a sulfuric acid solution and an oxidizing agent into the hafnium oxalate feed liquid, and reacting at a certain temperature to obtain the hafnium sulfate feed liquid. Oxidants used in the method are preferably hydrogen peroxide and ozone, other impurity ions are not introduced, and the purity of the product is not influenced at all. Oxidation products are H2O and CO2 and are basically free of pollution to the environment. The process of evaporation, filtration, calcination, redissolution and the like of a traditional evaporation method and an alkali precipitation-redissolution method is not needed, the operation is simple, the efficiency is high, the cost is low, and the operability is high. The method for adding the sulfuric acid solution and the oxidizing agent into the oxalate feed liquid is also suitable for converting oxalate solutions of other metal ions into sulfate solutions, including but not limited to zirconium oxalate, titanium oxalate, thorium oxalate, scandium oxalate, niobium oxalate, tantalum oxalate, vanadium oxalate, cobalt oxalate, cesium oxalate and rubidium oxalate.

Description

Technical Field

[0001] This invention belongs to the field of hydrometallurgy, and specifically relates to a method for converting hafnium oxalate feedstock into hafnium sulfate feedstock. Background Technology

[0002] Hafnium (Hf), a transition metal element in Group IVB of the 6th period, possesses excellent corrosion resistance, ductility, and high-temperature stability, and is widely used in various technological fields. In the electrical field, its low work function makes it an ideal choice for X-ray tube cathode materials; in the nuclear industry, thanks to its significant thermal neutron capture cross section (thermal neutron absorption cross section), hafnium is widely used as a core material for nuclear reactor control rods and radiation protection components; in the field of metallic materials, hafnium is often introduced as an alloying additive to significantly improve the overall performance of the matrix alloy.

[0003] Oxalate ion (C2O4) 2 Hafnium oxalate (-) is a high-affinity chelating ligand with extremely strong binding ability to metal ions. It is often used as a back-extraction agent for metal ions in solvent extraction and separation. Hafnium used in semiconductors and laser crystals requires extremely high purity, >99.99%. If further purification of hafnium oxalate back-extraction solutions to prepare high-purity hafnium is required, the extraction system must be converted to a suitable one. For example, organophosphate extractants (such as P204, P507, and Cyanex 272) preferentially extract hafnium in a sulfuric acid system, and the organophosphate-ketone-sulfuric acid-thiocyanate system is also preferentially extractive of hafnium, both suitable for purifying hafnium from high-hafnium feed solutions. If an extraction and separation system containing H2SO4 is used to further purify hafnium in hafnium oxalate feed solutions, it must first be converted to a sulfuric acid system before proceeding to the next extraction and separation step. The existing technology involves evaporating or precipitating hafnium oxalate back-extraction solution to obtain hafnium oxalate crystals or hafnium hydroxide precipitate, then calcining at high temperature to obtain hafnium oxide solid, and finally dissolving it to obtain hafnium sulfate solution. On January 2, 2025, Guangdong Pioneer Rare Materials Co., Ltd. submitted an invention patent application with application number CN202510004244.5 entitled "High-purity hafnium oxide and its preparation method", which mentions that "hafnium oxide powder is successively subjected to alkali melting, water leaching and filtration to obtain hafnium hydroxide filter cake; the hafnium hydroxide filter cake is dissolved in sulfuric acid solution to obtain hafnium sulfate solution". This method only aims to obtain hafnium sulfate solution from hafnium oxide solid, and involves multiple processes such as alkali melting, water leaching, filtration and sulfuric acid dissolution. The operation is complicated, energy-intensive, and water-intensive, and the wastewater generated further increases the cost. Obtaining hafnium oxide from hafnium oxalate feed solution using traditional evaporation crystallization or alkaline precipitation methods, and then preparing hafnium sulfate feed solution from hafnium oxide, both involve solid-liquid phase transition processes, requiring precipitation tanks and specialized facilities and sites for handling solid materials. This not only significantly increases fixed asset investment and operating space costs, but also, because the generated hafnium oxide has extremely low solubility in the aqueous phase and is chemically very stable, leads to lengthy reconstitution time, large acid consumption, and cumbersome, energy-intensive, inefficient, and costly operations. SUMMARY

[0004] The application provides a method for converting a hafnium oxalate solution into a hafnium sulfate solution, characterized in that a sulfuric acid solution and an oxidizing agent are added to the hafnium oxalate solution, and a reaction is carried out at a certain temperature to obtain a hafnium sulfate solution.

[0005] Further, the hafnium oxalate solution is a solution containing hafnium oxalate, and the solution can also contain oxalic acid and zirconium oxalate; if the hafnium oxalate solution contains zirconium oxalate, a mixed solution containing zirconium sulfate and hafnium sulfate is obtained.

[0006] Further, the hafnium sulfate solution is a sulfuric acid system solution containing Hf(SO4)2 and / or HfOSO4; and the mixed solution containing zirconium sulfate and hafnium sulfate is a sulfuric acid system solution containing Zr(SO4)2, ZrOSO4, Hf(SO4)2 and / or HfOSO4.

[0007] Further, the concentration of the sulfuric acid solution is 2-18.4 mol / L, and the concentration of H2SO4 in the hafnium oxalate solution after the addition of the sulfuric acid solution is 0.5-8 mol / L, preferably 1-3 mol / L. The sulfuric acid provides an acidic environment to inhibit the generation of hafnium hydroxide, and at the same time, hafnium sulfate is generated.

[0008] Further, the oxidizing agent is preferably one or more of hydrogen peroxide or ozone.

[0009] Further, the certain temperature is 0-120℃, preferably 25-100℃, which provides suitable conditions for the oxidation of oxalic acid / oxalate by the oxidizing agent.

[0010] Further, the hafnium sulfate solution can also be obtained by adding an oxidizing agent to the hafnium oxalate solution, carrying out a reaction at a certain temperature to obtain hafnium precipitate, dissolving the precipitate with a sulfuric acid solution, and obtaining a hafnium sulfate solution.

[0011] Key points of the application:

[0012] Compared with the comparative document CN202510004244.5, the comparative document obtains a hafnium sulfate solution through multiple processes such as hafnium oxide melting, water immersion, filtration, and sulfuric acid dissolution. The application obtains a hafnium sulfate solution from a hafnium oxalate stripping solution obtained in a zirconium-hafnium extraction separation process.

[0013] In the application, the oxidizing agent used does not introduce other impurity ions, and does not have any impact on the purity of the product. The oxidation product is H2O and CO2, which does not pollute the environment.

[0014] The present application does not involve a state transition, and does not produce insoluble solids. By adding a sulfuric acid solution and an oxidizing agent, the hafnium oxalate solution is directly converted into a hafnium sulfate solution, without liquid-solid or solid-liquid phase transition, and the reaction is kept in a liquid phase homogeneous environment throughout the process, avoiding the generation of solid intermediates in the traditional process, without filtration, washing and other processes, and the operation is very simple, greatly improving the production efficiency while keeping the production cost low.

[0015] The present application does not involve solid-liquid separation, high-temperature calcination, and multiple processes such as redissolution, and the equipment investment is low, the site requirement is small, and it can be directly integrated into the existing production system.

[0016] The method of adding a sulfuric acid solution and an oxidizing agent to the oxalate solution is also applicable to converting oxalate solutions of other metal ions into sulfate solutions, including but not limited to zirconium oxalate, titanium oxalate, thorium oxalate, scandium oxalate, niobium oxalate, tantalum oxalate, vanadium oxalate, cobalt oxalate, cesium oxalate, and rubidium oxalate. DETAILED DESCRIPTION

[0017] The method of the present application is further illustrated below in conjunction with examples. The examples of the present application are used to explain the present application and do not constitute an improper limitation on the present application.

[0018] Example 1

[0019] The liquid to be treated is a hafnium oxalate solution, and the concentrations of the components in the solution are Hf 6.92 g / L and oxalic acid 0.4 mol / L. 10 mL of the solution is taken and placed in a 50 mL centrifuge tube, a magnetic stirrer is added, and then placed in a water bath for heating. When the temperature rises to 95℃, the magnetic stirrer is turned on, and 1.2 mL of 30% H2O2 solution and 3 mL of 5 mol / L sulfuric acid solution are added dropwise. After the dropwise addition is completed, the reaction is continued for 2 h to obtain a hafnium sulfate solution.

[0020] 10 mL of the hafnium sulfate solution is taken in a beaker and subjected to redox titration using 0.01 mol / L KMnO4, and the residual oxalic acid concentration in the solution is measured to be about 0.008 mol / L.

[0021] Example 2

[0022] The liquid to be treated is a multi-stage stripping solution after stripping in a zirconium-hafnium separation industry, containing Zr 4.14 g / L, Hf 5.23 g / L, and oxalic acid 0.5 mol / L. 100 mL of the solution is taken and placed in a 500 mL flask, and heated to 80℃. Then 15 mL of 50% H2O2 solution and 9 mL of 98% concentrated H2SO4 are added in batches. After no bubbles are generated, heating and stirring are stopped, and a mixed solution of zirconium sulfate and hafnium sulfate is obtained.

[0023] Take 10 mL hafnium sulfate solution in a beaker, using 0.01 mol / L KMnO4 for redox titration, and the residual oxalic acid concentration in the solution is about 0.011 mol / L.

[0024] Example 3

[0025] The liquid to be treated is a Hf-containing solution in the production process of zirconium-hafnium extraction separation, the Hf concentration is 14.93 g / L, and the oxalic acid concentration is about 0.37 mol / L. Take 250 mL of the solution in a 500 mL beaker, add 22 mL of 98% concentrated sulfuric acid, and pass ozone into the solution at room temperature. After 3 h of reaction, stop the ozone passing, and obtain a hafnium sulfate solution.

[0026] Take 10 mL hafnium sulfate solution in a beaker, using 0.01 mol / L KMnO4 for redox titration, and the residual oxalic acid concentration in the solution is about 0.006 mol / L.

[0027] The above only describes the implementation examples of the patent, and does not limit the patent. For those skilled in the art, the patent can be variously changed and varied. Any modification, equivalent replacement and improvement within the spirit and principle of the patent should be included in the protection scope of the patent.

Claims

1. A process for converting a hafnium oxalate feed solution to a hafnium sulfate feed solution, characterized by, The hafnium oxalate solution is added with sulfuric acid solution and oxidant, and reacted at a certain temperature to obtain a hafnium sulfate solution.

2. The process for converting a feed of hafnium oxalate to a feed of hafnium sulfate according to claim 1, wherein, The hafnium oxalate solution is a solution containing hafnium oxalate, and can also contain oxalic acid and zirconium oxalate; if the hafnium oxalate solution contains zirconium oxalate, it is converted into a mixed solution containing zirconium sulfate and hafnium sulfate.

3. The process for converting a hafnium oxalate feed solution to a hafnium sulfate feed solution according to claim 1, wherein, The hafnium sulfate solution is a sulfuric acid system solution containing Hf(SO4)2 and / or HfOSO4; the mixed solution containing zirconium sulfate and hafnium sulfate is a sulfuric acid system solution containing Zr(SO4)2, ZrOSO4, Hf(SO4)2 and / or HfOSO4.

4. The method for converting a hafnium oxalate feed solution to a hafnium sulfate feed solution of claim 1, wherein, The concentration of the sulfuric acid solution is 2-18.4 mol / L, and the concentration of H2SO4 in the hafnium oxalate solution after adding the sulfuric acid solution is 0.5-8 mol / L, preferably 1-3 mol / L.

5. The process for converting a hafnium oxalate feed to a hafnium sulfate feed according to claim 1, wherein, The oxidant is preferably one or more of hydrogen peroxide or ozone.

6. The process for converting a feed of a hafnium oxalate to a feed of a hafnium sulfate according to claim 1, wherein, The certain temperature is 0-120℃.

7. The method for converting a hafnium oxalate feed solution to a hafnium sulfate feed solution according to claim 1 or 6, wherein, The certain temperature is 25-100℃.

8. The method of claim 1, wherein the method is characterized by, The hafnium sulfate solution can also be obtained by adding an oxidant to the hafnium oxalate solution, reacting at a certain temperature to obtain hafnium precipitate, dissolving the precipitate with sulfuric acid solution to obtain the hafnium sulfate solution.

9. The process for converting a feed of hafnium oxalate to a feed of hafnium sulfate of claim 1 wherein, The method of adding sulfuric acid solution and oxidant to the oxalate solution is also applicable to converting oxalate solutions of other metal ions into sulfate solutions, including but not limited to zirconium oxalate, titanium oxalate, thorium oxalate, scandium oxalate, niobium oxalate, tantalum oxalate, vanadium oxalate, cobalt oxalate, cesium oxalate and rubidium oxalate.