Solvent extraction system for separating zirconium and hafnium and preparation method, and method for separating zirconium and hafnium

Abstract

The embodiment of the application discloses a solvent extraction system for separating zirconium and hafnium, a preparation method thereof and a zirconium-hafnium separation method, relates to the rare metal separation technical field, and can solve the problems of the existing separation method, such as serious loss of extractant, small separation coefficient, inefficient separation of zirconium and hafnium, easy emulsification and large system acidity. The organic phase of the solvent extraction system for separating zirconium and hafnium comprises a methyl ketone extractant and an organic phosphorus / phosphonic acid extractant, wherein the methyl ketone extractant is a compound with the structure, R1 is an alkyl group containing 4-10 carbon atoms; the organic phosphorus / phosphonic acid extractant is a compound with the structure, R2 and R3 are alkyl groups, and the total number of carbon atoms in R2 and R3 is between 12 and 20. The aqueous phase of the solvent extraction system is a zirconium-hafnium acidic feed liquid at least comprising thiocyanate ions and sulfate ions.

Description

Technical Field

[0001] This disclosure relates to the field of rare metal separation technology, and in particular to a solvent extraction system for separating zirconium and hafnium, its preparation method, and a method for separating zirconium and hafnium. Background Technology

[0002] Zirconium (Zr) and hafnium (Hf) are important strategic metals widely used in nuclear industry, military, aerospace, medical devices, new materials science, and information industry. Due to the significant difference in their thermal neutron absorption cross-sections, zircon and hafnium have completely different applications in the nuclear industry, requiring deep separation for utilization. However, zircon and hafnium often coexist; for example, zircon, the main commercial source of zirconium, contains 1–3% hafnium, but nuclear-grade zirconium requires a hafnium content of less than 0.01%, and nuclear-grade hafnium requires a zirconium content of less than 2%. Furthermore, zirconium and hafnium are located in adjacent periods of the same group in the periodic table, possessing almost identical ionic radii and very similar physical and chemical properties. Therefore, deep separation of zirconium and hafnium presents a significant challenge.

[0003] Solvent extraction is the primary method for separating zirconium and hafnium in industry. Compared to fractional crystallization, molten salt distillation, and ion exchange, solvent extraction offers higher production capacity, lower cost, and ease of continuous production. The MIBK-HSCN system is the most commonly used solvent extraction system for separating zirconium and hafnium, producing sponge zirconium that accounts for two-thirds of global zirconium production. The MIBK-HSCN system preferentially extracts hafnium, which has a low content, achieving a zirconium-hafnium separation coefficient of 10–14. However, MIBK has a low flash point (22.78℃) and low boiling point (115.9℃), making it highly volatile during extraction, emitting an unpleasant odor, and flammable and explosive properties. It also has high solubility in water (1.70% at 25℃), leading to significant extractant loss during extraction. Furthermore, due to the low zirconium-hafnium separation coefficient of the MIBK-HSCN system, only nuclear-grade zirconium products can be obtained. Additionally, a large amount of zirconium is co-extracted into the organic phase, resulting in poor organic phase flowability. Heating is required during extraction, increasing energy consumption, exacerbating extractant volatilization, and worsening the operating environment.

[0004] Besides the MIBK-HSCN system, only the TOA-H2SO4 and TBP-HNO3-HCl systems are currently used for industrial production. Both of these separation systems preferentially extract zirconium with high content, but the former has a small extraction capacity, a long process flow, and a zirconium-hafnium separation coefficient of only 8-10; the latter is prone to emulsification, has high acidity, consumes a large amount of reagents, and is highly corrosive to equipment. Therefore, nuclear-grade zirconium produced by these two systems accounts for only a small portion of the global nuclear-grade zirconium market.

[0005] To address the drawbacks of MIBK, such as high water solubility, low flash point, and flammability, Professor Xu Zhigao's research group at South-Central University for Nationalities developed a diisobutyl ketone (DIBK)-HSCN extraction system. This system also preferentially extracts hafnium, but its extraction capacity is much lower than that of the MIBK-HSCN system, and the zirconium-hafnium separation coefficient is very low, only 1.23. To overcome the shortcomings of the DIBK-HSCN method in terms of weak zirconium-hafnium extraction capacity and low separation coefficient, Professor Xu's group further investigated extraction systems such as DIBK-P204, DIBK-Cyanex 572, DIBK-P350, and DIBK-TBP, but the highest zirconium-hafnium separation coefficient was only 17.6.

[0006] Therefore, developing a new solvent extraction system for the efficient separation of zirconium and hafnium is of great significance. Summary of the Invention

[0007] In view of this, the present disclosure provides a solvent extraction system for separating zirconium and hafnium and its preparation method, as well as a method for separating zirconium and hafnium, which can solve the problem in the prior art that the zirconium-hafnium separation coefficient is small and can only obtain nuclear-grade hafnium.

[0008] In addition, the solvent extraction system provided in this application can also solve the problems of the large amount of co-extracted zirconium in existing extraction systems, which leads to increased viscosity of the organic phase and thus requires heating, as well as the problems of the extractant being volatile, resulting in a poor operating environment and high risk. Furthermore, it is not easily emulsified, and the system has low acidity and will not corrode the equipment.

[0009] In a first aspect, embodiments of this disclosure provide a solvent extraction system for separating zirconium and hafnium, wherein the organic phase of the solvent extraction system comprises: a methyl ketone extractant and an organophosphorus / phosphonic acid extractant, wherein...

[0010] The methyl ketone extractant is a type of extractant with... Compounds with the structure R1 being an alkyl group containing 4 to 10 carbon atoms;

[0011] Organophosphorus / phosphonic acid extractants are those with Compounds with the structure R2 and R3 being alkyl groups, and the total number of carbon atoms in R2 and R3 being between 12 and 20;

[0012] The aqueous phase of the solvent extraction system is a zirconium-hafnium acidic feed solution containing at least thiocyanate and sulfate ions.

[0013] Optionally, the volume ratio of the organophosphorus / phosphonic acid extractant to the methyl ketone extractant is 0.01 to 0.5.

[0014] Optionally, the solvent extraction system further includes a diluent, wherein the volume ratio of the diluent to the methyl ketone extractant is less than 2.

[0015] Optionally, the methyl ketone extractant includes one or more of methyl isobutyl ketone, methyl isopentyl ketone, methyl isohexyl ketone, methyl isohexyl ketone, methyl isooctyl ketone, methyl isononyl ketone, methyl isodecyl ketone, methyl pentanyl ketone, methyl hexyl ketone, methyl heptayl ketone, methyl octyl ketone, methyl nonyl ketone, and methyl decyl ketone.

[0016] Optionally, the organophosphorus / phosphonic acid extractant includes one or more of the following: (2-ethylhexyl)(2,4,4-trimethylpentyl)phosphonic acid, (octyl)(2,4,4-trimethylpentyl)phosphonic acid, (2,3-dimethylbutyl)(2,4,4-trimethylpentyl)phosphonic acid, (2,4-dimethylheptyl)(2,4,4-trimethylpentyl)phosphonic acid, (2-ethylhexyl)(2,3-dimethylbutyl)phosphonic acid, (octyl)(2-ethylhexyl)phosphonic acid, bis(2,4,4-trimethylpentyl)phosphonic acid, bis(2-ethylhexyl)phosphonic acid, bis(octyl)phosphonic acid, 2-ethylhexyl phosphate mono-2-ethylhexyl ester, hexyl phosphate monodecyl ester, isopropyl phosphate monododecyl ester, bis(2-ethylhexyl) phosphate, and bis(1-methylheptyl) phosphate.

[0017] Optionally, the diluent includes one or more of alkanes, aromatics, kerosene, and sulfonated kerosene.

[0018] Optionally, the concentration of thiocyanate ions in the zirconium-hafnium acidic feed solution is 0.1–2.5 mol / L, the concentration of sulfate ions is 0.1–2 mol / L, and the concentration of hydrogen ions is 0.1–3 mol / L.

[0019] Secondly, embodiments of this disclosure provide a method for preparing a solvent extraction system, comprising: mixing a methyl ketone extractant, an organophosphorus / phosphonic acid extractant, and a diluent to form the organic phase of the solvent extraction system, wherein...

[0020] The methyl ketone extractant is a type of extractant with... Compounds with the structure R1 being an alkyl group containing 4 to 10 carbon atoms;

[0021] Organophosphorus / phosphonic acid extractants are those with Compounds with the structure R2 and R3 being alkyl groups, and the total number of carbon atoms in R2 and R3 being between 12 and 20;

[0022] The volume ratio of the organophosphorus / phosphonic acid extractant to the methyl ketone extractant is 0.01 to 0.5, and the volume ratio of the diluent to the methyl ketone extractant is less than 2.

[0023] The raw materials containing zirconium and hafnium are prepared into a zirconium-hafnium acidic feed solution containing at least thiocyanate ions and sulfate ions, and used as the aqueous phase of the solvent extraction system.

[0024] Optionally, the preparation method further includes: mixing the organic phase of the prepared solvent extraction system with a solution containing thiocyanate, so that the solvent extraction system is pre-loaded with thiocyanate. Optionally, the concentration of the solution containing thiocyanate is 0.1–3 mol / L.

[0025] Thirdly, embodiments of this disclosure also provide a method for separating zirconium and hafnium, comprising:

[0026] Choose any of the solvent extraction systems described above as the organic phase, or use the solvent extraction system prepared by the preparation method to extract the zirconium-hafnium acidic feed solution through the organic phase of the solvent extraction system to obtain a zirconium solution with a hafnium content of less than 0.01% and an organic phase loaded with zirconium-hafnium.

[0027] The organic phase loaded with zirconium and hafnium was washed with detergent to remove the loaded zirconium, resulting in a hafnium-containing organic solution with a zirconium content of less than 1%.

[0028] The obtained hafnium-containing organic solution was back-extracted using a back-extraction agent to obtain a hafnium solution with a zirconium content of less than 1%.

[0029] Optionally, in the step of organic phase extraction of zirconium-hafnium acidic feed solution, the ratio of organic phase to zirconium-hafnium acidic feed solution is 0.1 to 10, the extraction time is 1 to 60 min, the number of extraction stages is 1 to 20, and the extraction temperature is 0 to 50℃.

[0030] Optionally, in the step of washing the organic phase supported on zirconium and hafnium with detergent, the ratio of the organic phase supported on zirconium and hafnium to the detergent is 0.1 to 10, the washing time is 1 to 60 minutes, the number of washing stages is 1 to 10, and the washing temperature is 0 to 50°C.

[0031] Optionally, in the step of back-extracting the hafnium-containing organic solution with a back-extracting agent, the ratio of the hafnium-containing organic solution as the organic phase to the back-extracting agent is 0.1 to 10, the back-extraction time is 1 to 60 min, the number of back-extraction stages is 1 to 10, and the back-extraction temperature is 0 to 50°C.

[0032] Optionally, the detergent contains at least sulfate ions and hydrogen ions, wherein the concentration of sulfate ions can be 0.1–3 mol / L and the concentration of hydrogen ions can be 0.1–3 mol / L; the stripping agent comprises a 3–6 mol / L H2SO4 solution.

[0033] This invention provides a solvent extraction system for separating zirconium and hafnium. This system preferentially extracts hafnium, which has a lower content, and the zirconium-hafnium separation coefficient reaches over 70 for the first time, which is much greater than that of the MIBK-HSCN system (β). Hf / Zr=10-14) and other reported extraction systems have zirconium-hafnium separation coefficients (all less than 40); the co-extracted zirconium amount is small, the organic phase viscosity is low, heating is not required, and nuclear-grade zirconium and nuclear-grade hafnium products can be obtained simultaneously. In the solvent extraction system of this application, hydrogen bonds can be formed between organophosphorus / phosphonic acid extractants and methyl ketone extractants, making methyl ketone extractants less volatile, improving the operating environment, and reducing extractant loss during use; moreover, the solvent extraction system of this application does not exhibit emulsification and has low acidity.

[0034] The above description is merely an overview of the technical solution disclosed herein. In order to better understand the technical means of this disclosure and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of this disclosure more apparent and understandable, preferred embodiments are described below in detail with reference to the accompanying drawings. Attached Figure Description

[0035] To more clearly illustrate the technical solutions of the embodiments of this disclosure, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this disclosure. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0036] Figure 1 A flowchart illustrating a method for separating zirconium and hafnium according to an embodiment of this disclosure. Detailed Implementation

[0037] The present disclosure will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the scope of the disclosure. Furthermore, it should be noted that, for ease of description, only the parts relevant to the present disclosure are shown in the accompanying drawings.

[0038] It should be noted that, where there is no conflict, the embodiments and features described in this disclosure can be combined with each other. The technical solutions of this disclosure will now be described in detail with reference to the accompanying drawings and embodiments.

[0039] Unless otherwise stated, the exemplary implementations / embodiments shown are to be understood as providing exemplary features of various details that provide ways in which the technical concepts of this disclosure can be implemented in practice. Therefore, unless otherwise stated, the features of various implementations / embodiments may be additionally combined, separated, interchanged and / or rearranged without departing from the technical concepts of this disclosure.

[0040] The terminology used herein is for the purpose of describing particular embodiments and is not intended to be limiting. As used herein, unless the context clearly indicates otherwise, the singular forms “a” and “the” are intended to include the plural forms as well. Furthermore, when the terms “comprising” and / or “including” and variations thereof are used in this specification, it indicates the presence of the stated features, integrals, steps, operations, parts, components, and / or groups thereof, but does not exclude the presence or addition of one or more other features, integrals, steps, operations, parts, components, and / or groups thereof. It should also be noted that, as used herein, the terms “substantially,” “about,” and other similar terms are used as approximate terms rather than as terms of degree, thus explaining the inherent biases in measurements, calculated values, and / or provided values ​​that would be recognized by one of ordinary skill in the art.

[0041] Example 1

[0042] This embodiment provides a solvent extraction system for separating zirconium and hafnium, wherein the organic phase includes methyl ketone extractants and organophosphorus / phosphonic acid extractants, wherein...

[0043] The methyl ketone extractant is a type of extractant with... Compounds with the structure R1 being an alkyl group containing 4 to 10 carbon atoms;

[0044] Organophosphorus / phosphonic acid extractants are those with A compound with the structure R1, R2, and R3 being alkyl groups, and the total number of carbon atoms in R2 and R3 being between 12 and 20. R1, R2, and R3 may be the same as or different from each other.

[0045] The solvent extraction system provided in this application requires first preparing the raw materials containing zirconium and hafnium into an acidic zirconium-hafnium feed solution containing thiocyanate ions and sulfate ions, and then extracting the zirconium-hafnium acidic feed solution through the organic phase composed of the above-mentioned methyl ketone extractant and organophosphorus / phosphonic acid extractant.

[0046] The extraction method involves mixing an organic phase and an aqueous phase. The substance to be separated from the aqueous phase enters the organic phase, and the two phases are then separated by their different mass densities. In this application, the organic phase consists of methyl ketone extractants and organophosphorus / phosphonic acid extractants. A suitable amount of diluent may also be added depending on the specific circumstances; however, diluents are not essential. The aqueous phase in this application refers to a zirconium-hafnium acidic feed solution, in which the anions consist of at least thiocyanate ions, chloride ions, and sulfate ions.

[0047] The solvent extraction system provided in this application preferentially extracts hafnium, which has a low content, and the zirconium-hafnium separation coefficient reaches over 70 for the first time, which is much greater than that of the MIBK-HSCN system (β). Hf / Zr=10~14) and other reported extraction systems with zirconium-hafnium separation coefficients (all less than 40); co-extracted zirconium amount is small, organic phase viscosity is low, no heating is required, and nuclear-grade zirconium and nuclear-grade hafnium products can be obtained simultaneously; hydrogen bonds can be formed between organophosphorus / phosphonic acid extractants and methyl ketone extractants, which makes methyl ketone extractants less volatile, improves the operating environment, and reduces extractant loss during use; and the extractant has low acidity and does not produce emulsification.

[0048] The volume ratio of organophosphorus / phosphonic acid extractants to methyl ketone extractants can be 0.01 to 0.5.

[0049] When a diluent is added to the solvent extraction system, the volume ratio of the diluent to the methyl ketone extractant is less than 2.

[0050] The aforementioned methyl ketone extractants include, but are not limited to, one or more of the following: methyl isobutyl ketone, methyl isopentyl ketone, methyl isohexyl ketone, methyl isohexyl ketone, methyl isooctyl ketone, methyl isononyl ketone, methyl isodecyl ketone, methyl pentanyl ketone, methyl hexyl ketone, methyl heptayl ketone, methyl octyl ketone, methyl nonyl ketone, and methyl decyl ketone.

[0051] The aforementioned organophosphorus / phosphonic acid extractants include, but are not limited to, one or more of the following: (2-ethylhexyl)(2,4,4-trimethylpentyl)phosphonic acid, (octyl)(2,4,4-trimethylpentyl)phosphonic acid, (2,3-dimethylbutyl)(2,4,4-trimethylpentyl)phosphonic acid, (2,4-dimethylheptyl)(2,4,4-trimethylpentyl)phosphonic acid, (2-ethylhexyl)(2,3-dimethylbutyl)phosphonic acid, (octyl)(2-ethylhexyl)phosphonic acid, bis(2,4,4-trimethylpentyl)phosphonic acid, bis(2-ethylhexyl)phosphonic acid, bis(octyl)phosphonic acid, 2-ethylhexyl phosphate mono-2-ethylhexyl ester, hexyl phosphate monodecyl ester, isopropyl phosphate monododecyl ester, di(2-ethylhexyl) phosphate, and di(1-methylheptyl) phosphate.

[0052] The diluents mentioned above include, but are not limited to, one or more of alkanes, aromatics, kerosene, and sulfonated kerosene.

[0053] For example, the solvent extraction system of this embodiment can be composed of an organic phase consisting of 2-heptanone, xylene, and bis(2,4,4-trimethylpentyl)phosphonic acid (Cyanex 272). With a hafnium extraction rate >90%, the zirconium-hafnium separation coefficient can reach over 120, demonstrating excellent zirconium-hafnium separation performance. This significantly reduces the number of zirconium-hafnium extraction and separation stages during the separation process, thereby reducing investment in zirconium-hafnium separation equipment and site requirements.

[0054] The zirconium-hafnium acidic feed solution has a thiocyanate ion concentration of 0.1–2.5 mol / L, a sulfate ion concentration of 0.1–2 mol / L, and a hydrogen ion concentration of 0.1–3 mol / L. Some thiocyanate ions in the feed solution will combine with hydrogen ions to exist as thiocyanate; some sulfate ions will combine with hydrogen ions to exist as bisulfate ions. Therefore, the reduction in thiocyanate ion concentration due to the combination of some thiocyanate ions with hydrogen ions must be considered during preparation.

[0055] The concentration of zirconium in the above-mentioned zirconium-hafnium acidic feed solution can be 1-200 g / L, and the concentration of hafnium can be 0.001-50 g / L.

[0056] The solvent extraction system for separating zirconium and hafnium provided in this application has low acidity, no emulsification, and a high zirconium-hafnium separation coefficient, which can greatly reduce the number of zirconium-hafnium extraction and separation stages, and reduce investment in zirconium-hafnium separation equipment and site. During use, there is minimal extractant loss and volatilization, resulting in a low odor in the operating environment and making it environmentally friendly.

[0057] This disclosure also provides a method for preparing the above-mentioned solvent extraction system, comprising: mixing a methyl ketone extractant and an organophosphorus / phosphonic acid extractant in a certain proportion to form the organic phase of the solvent extraction system. The volume ratio of the organophosphorus / phosphonic acid extractant to the methyl ketone extractant is 0.01 to 0.5.

[0058] The methyl ketone extractant is a type of extractant with... Compounds with the structure R1 being an alkyl group containing 4 to 10 carbon atoms;

[0059] Organophosphorus / phosphonic acid extractants are those with Compounds with a structure in which R2 and R3 can be alkyl groups containing 6 to 10 carbon atoms, and R1, R2 and R3 may be the same as or different from each other.

[0060] The solvent extraction system described above can also be supplemented with a diluent, with the volume ratio of the diluent to the methyl ketone extractant being 0 to 2.

[0061] The aqueous phase of the solvent extraction system is an acidic zirconium-hafnium feed solution containing at least thiocyanate and sulfate ions. Specifically, the feed containing zirconium and hafnium can be prepared first into an acidic zirconium-hafnium feed solution containing thiocyanate and sulfate ions.

[0062] For example, the methyl ketone extractant may include one or more of methyl isobutyl ketone, methyl isopentyl ketone, methyl isohexyl ketone, methyl isohexyl ketone, methyl isooctyl ketone, methyl isononyl ketone, methyl isodecyl ketone, methyl pentanyl ketone, methyl hexyl ketone, methyl heptayl ketone, methyl octyl ketone, methyl nonyl ketone, and methyl decyl ketone.

[0063] For example, the organophosphorus / phosphonic acid extractant may include one or more of the following: (2-ethylhexyl)(2,4,4-trimethylpentyl)phosphonic acid, (octyl)(2,4,4-trimethylpentyl)phosphonic acid, (2,3-dimethylbutyl)(2,4,4-trimethylpentyl)phosphonic acid, (2,4-dimethylheptyl)(2,4,4-trimethylpentyl)phosphonic acid, (2-ethylhexyl)(2,3-dimethylbutyl)phosphonic acid, (octyl)(2-ethylhexyl)phosphonic acid, di(2,4,4-trimethylpentyl)phosphonic acid, di(2-ethylhexyl)phosphonic acid, di(octyl)phosphonic acid, 2-ethylhexyl phosphate mono-2-ethylhexyl ester, hexyl phosphate monodecyl ester, isopropyl phosphate monododecyl ester, di(2-ethylhexyl) phosphate, and di(1-methylheptyl) phosphate.

[0064] For example, the diluent may include one or more of alkanes, aromatics, kerosene, and sulfonated kerosene.

[0065] The solvent extraction system prepared according to the method of this application has low acidity, no emulsification, and a high zirconium-hafnium separation coefficient, which can greatly reduce the number of zirconium-hafnium extraction and separation stages, reduce investment in zirconium-hafnium separation equipment and site investment, and the extractant is not easily lost during use, making it environmentally friendly.

[0066] In some embodiments, the above preparation method may further include: mixing the organic phase of the prepared solvent extraction system with a solution containing thiocyanate, thereby preloading the solvent extraction system with thiocyanate. Optionally, the concentration of the thiocyanate-containing solution is 0.1–3 mol / L. The organic phase loaded with thiocyanate will improve the extraction separation coefficient of zirconium hafnium.

[0067] This disclosure also provides a method for separating zirconium and hafnium, using the aforementioned solvent extraction system, such as... Figure 1 As shown, the method includes:

[0068] Step 1: Extract the acidic zirconium-hafnium feed solution using an organic phase composed of a mixture of methyl ketone extractant and organophosphorus / phosphonic acid extractant, to obtain a zirconium solution with a hafnium content (Hf / (Hf+Zr)) of less than 0.01% and an organic phase loaded with zirconium and hafnium. Here, the hafnium content (Hf / (Hf+Zr)) refers to the mass ratio of hafnium contained in the zirconium solution to the total mass of hafnium and zirconium.

[0069] In this step, the solvent extraction system provided in any of the above embodiments is selected, and the zirconium-hafnium acidic feed solution is extracted by an organic phase composed of a mixture of methyl ketone extractant and organophosphorus / phosphonic acid extractant. The ratio of the organic phase to the zirconium-hafnium acidic feed solution is 0.1 to 10, the extraction time is 1 to 60 min, the number of extraction stages is 1 to 20, and the extraction temperature is 0 to 50°C.

[0070] In this step, the concentration of thiocyanate ions in the zirconium-hafnium acidic feed solution is 0.1–2.5 mol / L, the concentration of sulfate ions is 0.1–2 mol / L, and the concentration of hydrogen ions is 0.1–3 mol / L.

[0071] Step 2: Wash the above-mentioned organic phase loaded with zirconium and hafnium with detergent to remove the loaded zirconium and obtain a hafnium-containing organic solution with a zirconium content Zr / (Hf+Zr) of less than 1%. Here, the zirconium content Zr / (Hf+Zr) is the mass ratio of zirconium contained in the hafnium-containing organic solution to the total mass of hafnium and zirconium.

[0072] In this step, the ratio of the organic phase loaded with zirconium and hafnium to the detergent is 0.1 to 10, the washing time is 1 to 60 minutes, the number of washing stages is 1 to 10, and the washing temperature is 0 to 50°C.

[0073] Step 3: Back-extract the obtained hafnium-containing organic solution using a back-extraction agent to obtain a hafnium solution with a zirconium content (Zr / (Hf+Zr)) of less than 1%. Here, the zirconium content (Zr / (Hf+Zr)) is the mass ratio of zirconium in the hafnium solution to the total mass of hafnium and zirconium in the hafnium solution. In this step, both zirconium and hafnium in the organic phase are back-extracted to the aqueous phase to obtain a hafnium solution with a zirconium content (Zr / (Hf+Zr)) of less than 1%.

[0074] In this step, the ratio of the hafnium-containing organic solution as the organic phase to the stripping agent is 0.1 to 10, the stripping time is 1 to 60 min, the number of stripping stages is 1 to 10, and the stripping temperature is 0 to 50 °C.

[0075] Optionally, the detergent contains at least sulfate ions and hydrogen ions, wherein the concentration of sulfate ions may be 0.1–3 mol / L and the concentration of hydrogen ions may be 0.1–3 mol / L.

[0076] Optionally, the stripping agent mentioned above includes a 3-6 mol / L H2SO4 solution.

[0077] The zirconium-hafnium separation method provided in this application prioritizes the extraction of hafnium with lower content, and the zirconium-hafnium separation coefficient reaches more than 70 for the first time; the amount of zirconium co-extracted is small, the viscosity of the organic phase is low, no heating is required, and nuclear-grade zirconium and nuclear-grade hafnium products can be obtained simultaneously; the extractant is not easily volatilized during the separation process, and the operating environment is improved.

[0078] Example 2

[0079] The organic phase in this embodiment consists of 2-heptanone and 15 mmol / L (2-ethylhexyl)(2,4,4-trimethylpentyl)phosphonic acid; the aqueous phase contains Zr 1.85 g / L, Hf 106.5 mg / L, ammonium thiocyanate 2 mol / L, HCl 1.5 mol / L and ammonium sulfate 1.25 mol / L.

[0080] At room temperature, the above organic and aqueous phase solutions were mixed and shaken for 30 min at a ratio A / O = 2:1, and then allowed to stand for 20 min before separating the aqueous phase. The zirconium-hafnium separation coefficient was 72.55.

[0081] Example 3

[0082] The organic phase in this embodiment consists of 2-heptanone, xylene, and bis(2,4,4-trimethylpentyl)phosphonic acid (Cyanex 272), wherein the volume ratio of 2-heptanone to xylene is 10:1, and the concentration of Cyanex 272 is 5 mmol / L. The aqueous phase in this embodiment contains 2.5 g / L Zr, 62 mg / L Hf, 2 mol / L ammonium thiocyanate, 1.2 mol / L HCl, and 1 mol / L ammonium sulfate.

[0083] At room temperature, the above organic and aqueous phase solutions were mixed and shaken for 20 minutes at a ratio of A / O = 1:1, and then allowed to stand for 30 minutes before separating the aqueous phase. The zirconium-hafnium separation coefficient was as high as 124.

[0084] Example 4

[0085] The organic phase of this embodiment consists of 2-octanone, kerosene, and 2-ethylhexyl phosphate mono-2-ethylhexyl ester (P507), wherein the volume ratio of 2-octanone to kerosene is 3:1, and the concentration of P507 is 30 mmol / L. The aqueous phase of this embodiment contains 24.2 g / L Zr, 720 mg / L Hf, 2.5 mol / L thiocyanate, and 1.2 mol / L ammonium sulfate.

[0086] At room temperature, the above organic and aqueous phase solutions were mixed and shaken for 10 min at a ratio A / O = 1:2, and then allowed to stand for 15 min before separating the aqueous phase. The zirconium-hafnium separation coefficient was as high as 96.

[0087] In the description of this specification, the references to terms such as "one embodiment / mode," "some embodiments / modes," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment / mode or example is included in at least one embodiment / mode or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment / mode or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments / modes or examples. Furthermore, without contradiction, those skilled in the art can combine and integrate the different embodiments / modes or examples described in this specification, as well as the features of different embodiments / modes or examples.

[0088] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0089] Those skilled in the art should understand that the above embodiments are merely for illustrating the present disclosure and are not intended to limit the scope of the disclosure. Those skilled in the art can make other changes or modifications based on the above disclosure, and these changes or modifications still fall within the scope of the present disclosure.

Claims

1. A solvent extraction system for separating zirconium and hafnium, characterized in that, The organic phase of the solvent extraction system includes: methyl ketone extractants and organophosphorus / phosphonic acid extractants, wherein, The methyl ketone extractant is a type of extractant with... Compounds with the structure R1 being an alkyl group containing 4 to 10 carbon atoms; Organophosphorus / phosphonic acid extractants are those with or or Compounds with the structure R2 and R3 being alkyl groups, and the total number of carbon atoms in R2 and R3 being between 12 and 20; The aqueous phase of the solvent extraction system is a zirconium-hafnium acidic feed solution containing at least thiocyanate ions and sulfate ions. The volume ratio of the organophosphorus / phosphonic acid extractant to the methyl ketone extractant is 0.01~0.5; The solvent extraction system further includes a diluent, wherein the volume ratio of the diluent to the methyl ketone extractant is less than 2.

2. The solvent extraction system according to claim 1, characterized in that, The methyl ketone extractant includes one or more of the following: methyl isobutyl ketone, methyl isopentyl ketone, methyl isohexyl ketone, methyl isohexyl ketone, methyl isooctyl ketone, methyl isononyl ketone, methyl isodecyl ketone, methyl pentanyl ketone, methyl hexyl ketone, methyl heptayl ketone, methyl octyl ketone, methyl nonyl ketone, and methyl decyl ketone.

3. The solvent extraction system according to claim 1, characterized in that, The organophosphorus / phosphonic acid extractants include one or more of the following: (2-ethylhexyl)(2,4,4-trimethylpentyl)phosphonic acid, (octyl)(2,4,4-trimethylpentyl)phosphonic acid, (2,3-dimethylbutyl)(2,4,4-trimethylpentyl)phosphonic acid, (2,4-dimethylheptyl)(2,4,4-trimethylpentyl)phosphonic acid, (2-ethylhexyl)(2,3-dimethylbutyl)phosphonic acid, (octyl)(2-ethylhexyl)phosphonic acid, bis(2,4,4-trimethylpentyl)phosphonic acid, bis(2-ethylhexyl)phosphonic acid, bis(octyl)phosphonic acid, 2-ethylhexyl phosphate mono-2-ethylhexyl ester, hexyl phosphate monodecyl ester, isopropyl phosphate monododecyl ester, bis(2-ethylhexyl) phosphate, and bis(1-methylheptyl) phosphate.

4. The solvent extraction system according to claim 1, characterized in that, The diluent includes one or more of alkanes, aromatics, kerosene, and sulfonated kerosene.

5. The solvent extraction system according to claim 1, characterized in that, The concentration of thiocyanate ions in the zirconium-hafnium acidic feed solution is 0.1~2.5 mol / L, the concentration of sulfate ions is 0.1~2 mol / L, and the concentration of hydrogen ions is 0.1~3 mol / L.

6. A method for preparing a solvent extraction system, characterized in that, include: The organic phase of the solvent extraction system is prepared by mixing methyl ketone extractants, organophosphorus / phosphonic acid extractants, and diluents. The methyl ketone extractant is a type of extractant with... Compounds with the structure R1 being an alkyl group containing 4 to 10 carbon atoms; Organophosphorus / phosphonic acid extractants are those with or or Compounds with the structure R2 and R3 being alkyl, and the total number of carbon atoms in R2 and R3 being between 12 and 20; The volume ratio of the organophosphorus / phosphonic acid extractant to the methyl ketone extractant is 0.01~0.5, and the volume ratio of the diluent to the methyl ketone extractant is less than 2; The raw materials containing zirconium and hafnium are prepared into a zirconium-hafnium acidic feed solution containing at least thiocyanate ions and sulfate ions, and used as the aqueous phase of the solvent extraction system.

7. The preparation method according to claim 6, characterized in that, The organic phase of the prepared solvent extraction system is mixed with a solution containing thiocyanate to preload the solvent extraction system with thiocyanate. The concentration of the solution containing thiocyanate is 0.1~3 mol / L.

8. A method for separating zirconium and hafnium, characterized in that, include: Choose the solvent extraction system according to any one of claims 1-5, or the solvent extraction system prepared by the preparation method according to claim 6 or 7, and extract the zirconium-hafnium acidic feed solution through the organic phase of the solvent extraction system to obtain a zirconium solution with a hafnium content of less than 0.01% and an organic phase loaded with zirconium-hafnium; The organic phase loaded with zirconium and hafnium was washed with detergent to remove the loaded zirconium, resulting in a hafnium-containing organic solution with a zirconium content of less than 1%. The obtained hafnium-containing organic solution was back-extracted using a back-extraction agent to obtain a hafnium solution with a zirconium content of less than 1%.

9. The method for separating zirconium and hafnium according to claim 8, characterized in that, In the step of organic phase extraction of zirconium-hafnium acidic feed solution, the ratio of organic phase to zirconium-hafnium acidic feed solution is 0.1~10, the extraction time is 1~60 min, the number of extraction stages is 1~20, and the extraction temperature is 0~50 ℃; In the step of washing the organic phase of the zirconium-hafnium-supported ... In the step of back-extracting the obtained hafnium-containing organic solution with a back-extraction agent, the ratio of the hafnium-containing organic solution as the organic phase to the back-extraction agent is 0.1 to 10, the back-extraction time is 1 to 60 min, the number of back-extraction stages is 1 to 10, and the back-extraction temperature is 0 to 50 °C.

10. The method for separating zirconium and hafnium according to claim 8, characterized in that, The detergent contains at least sulfate ions and hydrogen ions, wherein the concentration of sulfate ions is 0.1~3 mol / L and the concentration of hydrogen ions is 0.1~3 mol / L; the stripping agent comprises a 3~6 mol / L H2SO4 solution.

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