A solvent extraction process for separating zirconium and hafnium

Abstract

The application provides a solvent extraction method for separating zirconium and hafnium. The method comprises the following steps: (1) providing an extraction feed solution; (2) performing countercurrent multistage extraction on the extraction feed solution by using a first organic phase to obtain a raffinate aqueous phase and a second organic phase, the mass ratio of zirconium to hafnium in the raffinate aqueous phase is less than or equal to 0.01%, the first organic phase comprises an extractant and a modifier, the extractant comprises at least one of tricyclohexylphosphine oxide, tri-n-butylphosphine oxide, tri-tert-butylphosphine oxide, triphenylphosphine oxide and Cyanex923; (3) performing countercurrent multistage washing on the second organic phase by using a washing solution to obtain a third organic phase, the mass ratio of hafnium to zirconium in the third organic phase is less than or equal to 1%; and (4) performing countercurrent multistage stripping on the third organic phase by using a stripping solution to obtain a fourth organic phase and a stripping aqueous phase, the concentration of hafnium and zirconium in the fourth organic phase is less than or equal to 0.01 mg / L, and the mass ratio of hafnium to zirconium in the stripping aqueous phase is less than or equal to 1%. Therefore, the zirconium and hafnium can be separated, the separation efficiency is high, and the method is environment-friendly.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of metal ion separation, in particular to a solvent extraction method for separating zirconium and hafnium. BACKGROUND

[0002] In nature, hafnium often coexists with zirconium, and minerals containing zirconium usually contain hafnium, and hafnium and zirconium are isomorphous. Zirconium and hafnium are extremely similar in chemical properties, and are difficult to separate.

[0003] The existing zirconium-hafnium separation process mainly includes two categories of pyrometallurgical process and hydrometallurgical process. Among them, the pyrometallurgical zirconium-hafnium separation process mainly includes molten salt rectification method and molten salt extraction method. The molten salt rectification method has a short process flow, but the process operation temperature is high, the energy consumption is large, and the equipment cost is high; the molten salt extraction method has low separation efficiency, and is difficult to meet the requirements of industrial application. The hydrometallurgical separation process of zirconium and hafnium mainly is solvent extraction process. Although the traditional extractant methyl isobutyl ketone (MIBK) can realize the selective extraction separation of zirconium and hafnium, the separation efficiency is low, and the purity of the produced zirconium and hafnium products is low; at the same time, because of the use of thiocyanic acid, it will cause serious environmental pollution.

[0004] Therefore, the method for separating zirconium and hafnium still needs to be improved. SUMMARY

[0005] The present application aims to at least partially alleviate or solve at least one of the above-mentioned problems.

[0006] In one aspect of the present application, the present application provides a solvent extraction method for separating zirconium and hafnium. In some embodiments of the present application, the solvent extraction method for separating zirconium and hafnium comprises: (1) providing an extraction feed solution, the extraction feed solution being an acidic solution containing zirconium elements and hafnium elements; (2) countercurrently multi-stage extracting the extraction feed solution with a first organic phase to obtain a raffinate aqueous phase and a second organic phase, the mass ratio of zirconium elements to hafnium elements in the raffinate aqueous phase being ≤0.01%, the first organic phase comprising an extractant and a modifier, the extractant comprising at least one of tricyclohexylphosphine oxide, tri-n-butylphosphine oxide, tri-tert-butylphosphine oxide, triphenylphosphine oxide, Cyanex923, the modifier comprising at least one of amyl acetate, diethyl carbonate, tributyl phosphate, ethyl benzoate, the concentration of the extractant in the first organic phase being 0.01mol / L-3mol / L; (3) countercurrently multi-stage washing the second organic phase with a washing solution to obtain a third organic phase, the mass ratio of hafnium elements to zirconium elements in the third organic phase being ≤1%, the washing solution comprising hydrochloric acid and / or nitric acid, the acidity of the washing solution being 0.1mol / L-4mol / L; (4) countercurrently multi-stage stripping the third organic phase with a stripping solution to obtain a fourth organic phase and a stripping aqueous phase, the concentration of both hafnium elements and zirconium elements in the fourth organic phase being ≤0.01mg / L, the mass ratio of hafnium elements to zirconium elements in the stripping aqueous phase being ≤1%, the stripping solution comprising hydrochloric acid and / or nitric acid, the acidity of the stripping solution being 0.01mol / L-2mol / L. Thus, zirconium and hafnium can be separated by using the above method, the separation efficiency is high, and the materials used in the method are environmentally friendly.

[0007] In some embodiments of the present application, the extraction feed solution satisfies at least one of the following conditions: the concentration of zirconium elements in the extraction feed solution is 0.001g / L-500g / L; the concentration of hafnium elements in the extraction feed solution is 0.001g / L-500g / L; the acidity of the extraction feed solution is 0.5mol / L-6mol / L.

[0008] In some embodiments of the present application, the extraction feed solution is obtained by dissolving a precursor containing hafnium elements and zirconium elements in an acid solution, the precursor comprising inorganic salts containing hafnium elements and zirconium elements and / or oxides containing hafnium elements and zirconium elements, the acid solution comprising hydrochloric acid and / or nitric acid.

[0009] In some embodiments of the present application, in step (2), the volume content of the modifier in the first organic phase is 5%-75%. Thus, it is beneficial to improve the extraction efficiency.

[0010] In some embodiments of the present application, the first organic phase further comprises a diluent, and the diluent comprises at least one of n-octanol, sec-octanol, n-dodecane, sulfonated kerosene, hydrogenated kerosene, n-hexane, n-heptane, cyclohexane, petroleum ether, toluene.

[0011] In some embodiments of the present application, in step (2), the volume ratio of the first organic phase to the raffinate is 0.5:1 to 3:1; and / or, in step (2), the number of stages of the countercurrent multi-stage extraction is ≥ 5 stages.

[0012] In some embodiments of the present application, in step (3), the volume ratio of the second organic phase to the washing liquid is 0.5:1 to 3:1; and / or, in step (3), the number of stages of the countercurrent multi-stage washing is ≥ 3 stages.

[0013] In some embodiments of the present application, in step (4), the volume ratio of the third organic phase to the stripping liquid is 0.5:1 to 3:1; and / or, in step (4), the number of stages of the countercurrent multi-stage stripping is ≥ 4 stages.

[0014] In some embodiments of the present application, the concentration of hafnium element in the raffinate aqueous phase obtained in step (2) is 0.001 g / L to 500 g / L.

[0015] In some embodiments of the present application, the concentration of zirconium element in the stripping aqueous phase obtained in step (4) is 0.001 g / L to 500 g / L. BRIEF DESCRIPTION OF DRAWINGS

[0016] The above and / or additional aspects and advantages of the present application will become apparent and be readily appreciated from the following description, including the appended drawings, wherein:

[0017] Figure 1 A solvent extraction flow diagram for separating zirconium and hafnium according to an embodiment of the present application is shown. DETAILED DESCRIPTION

[0018] Embodiments of the present application are described in detail below with reference to the attached drawing figures, wherein the same or like reference numerals are used throughout the drawing figures to refer to the same or like elements or elements having the same or similar functionality. The embodiments described below are merely exemplary for the purposes of explanation and are not intended to limit the application, which is limited only by the claims.

[0019] In one aspect of the present application, the present application provides a solvent extraction method for separating zirconium and hafnium. In some embodiments of the present application, with reference to Figure 1 , the solvent extraction method for separating zirconium and hafnium can comprise the following steps:

[0020] (1) providing a raffinate.

[0021] In some embodiments of the present application, the feed solution is an acidic solution containing zirconium element and hafnium element.

[0022] In some embodiments of the present application, the feed solution can be obtained by dissolving a precursor containing hafnium element and zirconium element in an acid solution. The precursor is dissolved in the acid solution to form an aqueous phase, and then extracted by an organic phase to separate the zirconium element and the hafnium element.

[0023] In some embodiments of the present application, the precursor can be a mineral containing hafnium element and zirconium element.

[0024] In some embodiments of the present application, the precursor can include inorganic salts containing hafnium element and zirconium element and / or oxides containing hafnium element and zirconium element. In some specific embodiments of the present application, the precursor can include chlorides, nitrates, etc. containing hafnium element and zirconium element. In other specific embodiments of the present application, the precursor can include oxides containing hafnium element and zirconium element.

[0025] In some embodiments of the present application, the acid solution can include hydrochloric acid and / or nitric acid. In some specific embodiments of the present application, the acid solution can be hydrochloric acid or nitric acid, and the concentrated hydrochloric acid or concentrated nitric acid can be diluted with water to form an acid solution, and then the precursor containing hafnium element and zirconium element is dissolved in the acid solution to obtain the feed solution.

[0026] In some embodiments of the present application, the concentration of zirconium element in the feed solution can be 0.001 g / L to 500 g / L, for example, the concentration of zirconium element can be 0.001 g / L, 0.01 g / L, 0.1 g / L, 1 g / L, 10 g / L, 30 g / L, 50 g / L, 100 g / L, 200 g / L, 500 g / L, etc.

[0027] In some embodiments of the present application, the concentration of hafnium element in the feed solution can be 0.001 g / L to 500 g / L, for example, the concentration of hafnium element can be 0.001 g / L, 0.05 g / L, 0.1 g / L, 0.5 g / L, 1 g / L, 20 g / L, 80 g / L, 100 g / L, 200 g / L, 500 g / L, etc.

[0028] In some embodiments of the present application, the acidity of the feed solution can be 0.5 mol / L to 6 mol / L, for example, the acidity of the feed solution can be 0.5 mol / L, 0.8 mol / L, 1 mol / L, 2 mol / L, 4 mol / L, 5 mol / L, 6 mol / L, etc.

[0029] (2) countercurrent multi-stage extraction of the feed solution with the first organic phase to obtain a raffinate aqueous phase and a second organic phase.

[0030] In this step, the mass ratio of zirconium element to hafnium element in the obtained raffinate aqueous phase is ≤0.01%, and the raffinate aqueous phase is used as a hafnium product, in which the content of zirconium element is very small, and the purity of the hafnium product is relatively high.

[0031] In some embodiments of the present application, the first organic phase can include an extractant and a modifier, wherein the extractant can include at least one of tricyclohexylphosphine oxide, tri-n-butylphosphine oxide, tri-tert-butylphosphine oxide, triphenylphosphine oxide, Cyanex923, and the modifier can include at least one of amyl acetate, diethyl carbonate, tributyl phosphate, ethyl benzoate. The above-mentioned extractant can selectively dissolve the target substance, so as to transfer it from the aqueous phase to the organic phase, which can increase the concentration of the target substance in the organic phase and improve the separation efficiency; the above-mentioned modifier can reduce the emulsification phenomenon between the organic phase and the aqueous phase, which is helpful for clear separation of the two phases, thereby further improving the extraction efficiency.

[0032] In some embodiments of the present application, the concentration of the extractant in the first organic phase can be 0.01mol / L-3mol / L, for example, the concentration of the extractant in the first organic phase can be 0.01mol / L, 0.05mol / L, 0.1mol / L, 0.5mol / L, 1mol / L, 2mol / L, 3mol / L, etc., thereby the hafnium and zirconium in the extraction stock solution can be made to enter the aqueous phase and the organic phase respectively by extraction, so as to achieve the purpose of separating hafnium and zirconium.

[0033] In some embodiments of the present application, in step (2), the volume content of the modifier in the first organic phase can be 5%-75%, for example, the volume content of the modifier in the first organic phase can be 5%, 10%, 25%, 50%, 75%, etc., and the content of the modifier in the above range is advantageous to improve the extraction efficiency and capacity (the capacity of metal ions in the organic phase, mainly zirconium ions).

[0034] In some embodiments of the present application, in addition to the extractant and the modifier, the first organic phase can also include a diluent, and the diluent can include at least one of n-octanol, sec-octanol, n-dodecane, sulfonated kerosene, hydrogenated kerosene, n-hexane, n-heptane, cyclohexane, petroleum ether, toluene. The above-mentioned diluent is not miscible with water, and in the extraction process, the components in the container can form two different phases, thereby being more advantageous to realize the separation of zirconium and hafnium.

[0035] In some embodiments of the present application, in step (2), the volume ratio of the first organic phase to the extraction stock solution can be 0.5:1-3:1, for example, the volume ratio of the first organic phase to the extraction stock solution can be 0.5:1, 1:1, 1.5:1, 2:1, 3:1, etc., thereby the organic phase can better dissolve the target component, thereby being advantageous to improve the extraction efficiency.

[0036] In some embodiments of the present application, in step (2), the number of stages of countercurrent multi-stage extraction can be ≥5 stages, for example, the number of stages of countercurrent multi-stage extraction can be 5 stages, 6 stages, 7 stages, etc. Through countercurrent multi-stage extraction, zirconium and hafnium can be more effectively separated, and more hafnium elements enter the aqueous phase, and zirconium elements enter the organic phase.

[0037] In some embodiments of the present application, the concentration of hafnium elements in the raffinate aqueous phase obtained in step (2) can be 0.001 g / L to 500 g / L, for example, the concentration of hafnium elements in the raffinate aqueous phase can be 0.005 g / L, 0.01 g / L, 0.05 g / L, 0.1 g / L, 0.5 g / L, 5 g / L, 50 g / L, 100 g / L, 400 g / L, etc.

[0038] After the extraction section, the original extraction solution can be divided into a raffinate aqueous phase and a second organic phase. The raffinate aqueous phase is the hafnium product, and the second organic phase enters the washing section for subsequent processing.

[0039] (3) The second organic phase is subjected to countercurrent multi-stage washing with a washing liquid to obtain a third organic phase.

[0040] Through countercurrent multi-stage washing of the second organic phase with a washing liquid, impurities in the second organic phase can be removed, and the impurities can be transferred to the aqueous phase. In the washing section, the separated organic phase is the third organic phase, and the separated aqueous phase can be returned to the extraction section for extraction again.

[0041] In some embodiments of the present application, the washing liquid used in the washing section can include hydrochloric acid and / or nitric acid, and the acidity of the washing liquid can be 0.1 mol / L to 4 mol / L. For example, the washing liquid can be hydrochloric acid or nitric acid, or a mixture of hydrochloric acid and nitric acid, and the acidity of the washing liquid can be 0.1 mol / L, 0.5 mol / L, 1 mol / L, 2 mol / L, 2.5 mol / L, 3 mol / L, 4 mol / L, etc. Using the above washing liquid to perform countercurrent multi-stage washing on the second organic phase can effectively remove impurities in the second organic phase, and facilitate obtaining a zirconium product with higher purity.

[0042] In some embodiments of the present application, the mass ratio of hafnium elements to zirconium elements in the third organic phase can be ≤1%, for example, the mass ratio of hafnium elements to zirconium elements in the third organic phase can be 1%, 0.5%, 0.2%, 0.1%, 0.05%, etc. The purity of zirconium elements in the third organic phase is relatively high, which is conducive to improving the purity of the finally prepared zirconium product.

[0043] In some embodiments of the present application, in step (3), the volume ratio of the second organic phase to the washing liquid can be 0.5:1 to 3:1, for example, the volume ratio of the second organic phase to the washing liquid can be 0.5:1, 1:1, 2:1, 3:1, etc., thereby the impurities in the organic phase can be transferred to the aqueous phase by washing, so as to facilitate improving the purity of zirconium in the organic phase.

[0044] In some embodiments of the present application, in step (3), the number of stages of countercurrent multi-stage washing can be ≥3 stages, for example, the second organic phase can be subjected to countercurrent washing for 3 stages, 4 stages, 5 stages or even more stages, thereby reducing the amount of impurities in the organic phase.

[0045] (4) subjecting the third organic phase to countercurrent multi-stage stripping with the stripping liquid to obtain a fourth organic phase and a stripping aqueous phase.

[0046] In some embodiments of the present application, the stripping liquid can comprise hydrochloric acid and / or nitric acid, and the acidity of the stripping liquid can be 0.01 mol / L to 2 mol / L, for example, the stripping liquid can be hydrochloric acid, nitric acid or a mixture of hydrochloric acid and nitric acid, and the acidity of the stripping liquid can be 0.01 mol / L, 0.05 mol / L, 0.1 mol / L, 0.5 mol / L, 1 mol / L, 2 mol / L, etc. Thus, the third organic phase can be subjected to countercurrent multi-stage stripping with the stripping liquid, so as to transfer more zirconium elements to the aqueous phase.

[0047] In some embodiments, concentrated nitric acid or concentrated hydrochloric acid can be diluted with water to prepare the stripping liquid.

[0048] In some embodiments of the present application, the concentrations of hafnium elements and zirconium elements in the fourth organic phase obtained after the stripping section are both ≤0.01 mg / L, the mass ratio of hafnium elements to zirconium elements in the stripping aqueous phase is ≤1%, the purity of zirconium elements in the stripping aqueous phase is high, and the amount of hafnium elements is extremely small, and the amounts of hafnium elements and zirconium elements in the fourth organic phase are extremely small. Therefore, it can be known that the hafnium elements and zirconium elements in the original leaching liquid are basically extracted into the raffinate aqueous phase and the stripping aqueous phase after the treatment of the extraction section, the washing section and the stripping section, the utilization rate of raw materials is high, the extraction efficiency is high, and the fourth organic phase can be reused as the organic phase of the extraction section.

[0049] In some embodiments of the present application, in step (4), the volume ratio of the third organic phase to the stripping liquid can be 0.5:1 to 3:1, for example, the volume ratio of the third organic phase to the stripping liquid can be 0.5:1, 0.8:1, 1:1, 1.5:1, 2.5:1, 3:1, etc., thereby facilitating stripping the zirconium elements in the organic phase into the aqueous phase to obtain the stripping aqueous phase with high zirconium content and high purity.

[0050] In some embodiments of the present application, the number of stages of the countercurrent multi-stage stripping in step (4) can be ≥4 stages, for example, the third organic phase can be subjected to 4-stage, 5-stage, 6-stage or even more stages of countercurrent stripping, so as to strip more zirconium elements into the aqueous phase.

[0051] In some embodiments of the present application, the concentration of zirconium elements in the stripping aqueous phase obtained in step (4) can be 0.001 g / L to 500 g / L, for example, the concentration of zirconium elements in the stripping aqueous phase can be 0.001 g / L, 0.01 g / L, 0.1 g / L, 1 g / L, 50 g / L, 200 g / L, 500 g / L, etc.

[0052] In general, the method proposed in the present application can separate hafnium and zirconium when treating the zirconium and hafnium-containing raw extraction solution, the separation efficiency is high, the purity of the obtained hafnium product and zirconium product is high, and the use of thiocyanic acid is not required, which is more friendly to the environment, and the organic phase can be reused.

[0053] The present application will be described below through specific examples, and those skilled in the art can understand that the specific examples below are only for illustrative purposes, and do not limit the scope of the present application in any way. In addition, in the following examples, unless otherwise specified, the materials and equipment used are commercially available. If the specific treatment conditions and methods are not explicitly described in the following examples, the conditions and methods known in the art can be used for treatment.

[0054] Example 1

[0055] Zirconium tetrachloride and hafnium tetrachloride were dissolved in hydrochloric acid to prepare a raw extraction solution, wherein the content of zirconium was 10 g / L, the content of hafnium was 15 g / L, and the acidity was 3 mol / L.

[0056] Tricyclohexylphosphine oxide (extractant) and pentyl acetate (modifier) were dissolved in n-octanol (diluent) to prepare a first organic phase, wherein the concentration of tricyclohexylphosphine oxide was 1 mol / L, and the volume content of pentyl acetate was 20%. Concentrated hydrochloric acid was diluted with water to obtain a washing liquid with an acidity of 3 mol / L. Concentrated hydrochloric acid was diluted with water to obtain a stripping liquid with an acidity of 0.1 mol / L.

[0057] The raffinate aqueous phase and the first organic phase are countercurrently extracted, the volume ratio of the raffinate aqueous phase to the first organic phase is 1:1, and 8 stages of extraction are performed to obtain a second organic phase and a raffinate aqueous phase; the second organic phase (loaded organic phase) is countercurrently and multi-staged washed with a washing liquid to obtain a third organic phase; the third organic phase (washed organic phase) is countercurrently and multi-staged stripped with a stripping liquid to obtain a stripping aqueous phase. Finally, the content of zirconium in the raffinate aqueous phase is 0.001 g / L, the content of hafnium is 12 g / L, and the mass ratio of zirconium to hafnium is 0.0083%; the content of zirconium in the stripping aqueous phase is 9.99 g / L, the content of hafnium is 0.02 g / L, and the mass ratio of hafnium to zirconium is 0.2%.

[0058] Example 2

[0059] Zirconium nitrate and hafnium tetrachloride are dissolved in nitric acid to prepare a raffinate aqueous phase, wherein the content of zirconium is 1 g / L, the content of hafnium is 200 g / L, and the acidity is 3 mol / L.

[0060] Cyanex923 (extractant) and ethyl benzoate (modifier) are dissolved in n-octanol (diluent) to prepare a first organic phase, wherein the concentration of Cyanex923 in the first organic phase is 0.1 mol / L, and the volume content of ethyl benzoate is 10%. Concentrated nitric acid is diluted with water to obtain a washing liquid with an acidity of 0.5 mol / L. Concentrated nitric acid is diluted with water to obtain a stripping liquid with an acidity of 1 mol / L.

[0061] The raffinate aqueous phase and the first organic phase are countercurrently extracted, the volume ratio of the raffinate aqueous phase to the first organic phase is 1:1, and 6 stages of extraction are performed to obtain a second organic phase and a raffinate aqueous phase; the second organic phase (loaded organic phase) is countercurrently and multi-staged washed with a washing liquid to obtain a third organic phase; the third organic phase (washed organic phase) is countercurrently and multi-staged stripped with a stripping liquid to obtain a stripping aqueous phase. Finally, the content of zirconium in the raffinate aqueous phase is 0.001 g / L, the content of hafnium is 199.99 g / L, and the mass ratio of zirconium to hafnium is 0.0005%; the content of zirconium in the stripping aqueous phase is 0.999 g / L, the content of hafnium is 0.01 g / L, and the mass ratio of hafnium to zirconium is 1%.

[0062] Example 3

[0063] Zirconium nitrate and hafnium tetrachloride are dissolved in nitric acid to prepare a raffinate aqueous phase, wherein the content of zirconium is 20 g / L, the content of hafnium is 10 g / L, and the acidity is 3 mol / L.

[0064] The first organic phase is prepared by dissolving tri-n-butylphosphine oxide (extractant) and tributylphosphine acid (modifier) in kerosene (diluent), wherein the concentration of tri-n-butylphosphine oxide is 1 mol / L and the volume content of tributylphosphine acid is 50%. Concentrated nitric acid is diluted with water to obtain a washing liquid with an acidity of 2 mol / L. Concentrated nitric acid is diluted with water to obtain a stripping liquid with an acidity of 0.01 mol / L.

[0065] The crude extract and the first organic phase are countercurrently extracted in a 10-stage extraction with a volume ratio of 1:1 to obtain a raffinate aqueous phase and a second organic phase. The second organic phase (loaded organic phase) is countercurrently washed with the washing liquid in a multi-stage washing to obtain a third organic phase. The third organic phase (washed organic phase) is countercurrently stripped with the stripping liquid in a multi-stage stripping to obtain a stripping aqueous phase. Finally, the content of zirconium in the raffinate aqueous phase is 0.001 g / L, the content of hafnium is 9.96 g / L, and the mass ratio of zirconium to hafnium is 0.01%. The content of zirconium in the stripping aqueous phase is 19.999 g / L, the content of hafnium is 0.04 g / L, and the mass ratio of hafnium to zirconium is 0.2%.

[0066] In the description of the present specification, the description of the terms "one embodiment", "some embodiments”, "some specific embodiments” and the like means that the specific features, structures, materials or characteristics described in connection with the embodiments are included in at least one embodiment of the present application. In the present specification, the illustrative description of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any appropriate manner in any one or more embodiments or examples. In addition, the different embodiments or examples described in the present specification and the features of the different embodiments or examples can be combined and combined by those skilled in the art without contradiction. In addition, it should be noted that in the present specification, the terms "first", "second", "third", "fourth" are for descriptive purposes only and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features.

[0067] Although the embodiments of the present application have been shown and described above, it should be understood that the above embodiments are exemplary and cannot be understood as limiting the present application, and those skilled in the art can make changes, modifications, replacements and variations to the above embodiments within the scope of the present application.

Claims

1. A solvent extraction method for separating zirconium and hafnium, characterized in that, include: (1) Provide an extraction solution, wherein the extraction solution is an acidic solution containing zirconium and hafnium; (2) The first organic phase is used to perform countercurrent multi-stage extraction on the extraction solution to obtain a raffinate aqueous phase and a second organic phase. The mass ratio of zirconium to hafnium in the raffinate aqueous phase is ≤0.01%. The first organic phase includes an extractant and a modifier. The extractant includes at least one of tricyclohexylphosphine oxide, tri-n-butylphosphine oxide, tri-tert-butylphosphine oxide, triphenylphosphine oxide, and Cyanex 923. The modifier includes at least one of amyl acetate, diethyl carbonate, tributyl phosphate, and ethyl benzoate. The concentration of the extractant in the first organic phase is 0.01 mol / L to 3 mol / L. (3) The second organic phase is subjected to countercurrent multi-stage washing with washing liquid to obtain a third organic phase, wherein the mass ratio of hafnium to zirconium in the third organic phase is ≤1%, and the washing liquid includes hydrochloric acid and / or nitric acid, and the acidity of the washing liquid is 0.1 mol / L to 4 mol / L; (4) The third organic phase is subjected to countercurrent multi-stage back-extraction with back-extraction solution to obtain a fourth organic phase and a back-extraction aqueous phase. The concentrations of hafnium and zirconium in the fourth organic phase are both ≤0.01 mg / L, and the mass ratio of hafnium to zirconium in the back-extraction aqueous phase is ≤1%. The back-extraction solution includes hydrochloric acid and / or nitric acid, and the acidity of the back-extraction solution is 0.01 mol / L to 2 mol / L. In step (2), the volume content of the modifier in the first organic phase is 5% to 75%.

2. The method according to claim 1, characterized in that, The extract solution meets at least one of the following conditions: The concentration of zirconium in the extraction solution is 0.001 g / L to 500 g / L; The concentration of hafnium in the extraction solution is 0.001 g / L to 500 g / L; The acidity of the extraction solution is 0.5 mol / L to 6 mol / L.

3. The method according to claim 1, characterized in that, The extraction solution is obtained by dissolving a precursor containing hafnium and zirconium in an acid solution. The precursor includes an inorganic salt containing hafnium and zirconium and / or an oxide containing hafnium and zirconium. The acid solution includes hydrochloric acid and / or nitric acid.

4. The method according to claim 1, characterized in that, The first organic phase further includes a diluent, which includes at least one of n-octanol, sec-octanol, n-dodecane, sulfonated kerosene, hydrogenated kerosene, n-hexane, n-heptane, cyclohexane, petroleum ether, and toluene.

5. The method according to any one of claims 1 to 4, characterized in that, In step (2), the volume ratio of the first organic phase to the extraction solution is 0.5:1 to 3:1; And / or, in step (2), the number of stages of the countercurrent multistage extraction is ≥5 stages.

6. The method according to any one of claims 1 to 4, characterized in that, In step (3), the volume ratio of the second organic phase to the washing liquid is 0.5:1 to 3:1; And / or, in step (3), the number of stages of the countercurrent multi-stage washing is ≥3 stages.

7. The method according to any one of claims 1 to 4, characterized in that, In step (4), the volume ratio of the third organic phase to the back-extraction solution is 0.5:1 to 3:1; And / or, in step (4), the number of stages of the countercurrent multi-stage back-extraction is ≥4 stages.

8. The method according to any one of claims 1 to 4, characterized in that, The concentration of hafnium in the aqueous raffinate obtained in step (2) is 0.001 g / L to 500 g / L.

9. The method according to any one of claims 1 to 4, characterized in that, The concentration of zirconium in the back-extraction aqueous phase obtained in step (4) is 0.001 g / L to 500 g / L.

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