Method and device for separating similar metal pairs through molten salt electrolysis

Abstract

The invention discloses a method and device for separating similar metal pairs through molten salt electrolysis. The method comprises the steps that a cylindrical inert metal electrode serves as a first cathode; a similar metal pair mixture is used as a first anode, the first anode is composed of high-activity metal and low-activity metal, and the content of the low-activity metal is larger than that of the high-activity metal; eutectic sodium sylvite or eutectic lithium sylvite containing low-activity metal high-valence salt serves as molten salt electrolyte and is placed in a first cathode, a first anode is arranged at the center axis of the first cathode, and first-time constant-current electrolysis is carried out; the high-activity metal atoms and the low-activity metal atoms sequentially enter the molten salt electrolyte in an ion form, and are further reduced and deposited on the surface of the inner wall of the cylindrical inert metal electrode in an alloy form; and the cylindrical inert metal electrode deposited with the alloy serves as a second anode, the first anode serves as a second cathode, second-time constant-current electrolysis is conducted, the high-activity metal is dissolved into the molten salt electrolyte, and separation of the high-activity metal and the low-activity metal is achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of electrochemical metallurgy, and in particular relates to a method and a device for separating similar metal pairs by molten salt electrolysis. Background Art

[0002] Metal separation technology is of great significance in the fields of mineral processing, metallurgical industry, environmental protection and resource recovery. Similar metal pairs (such as zirconium and hafnium, tantalum and niobium, titanium and vanadium, and tungsten and molybdenum) have similar physical and chemical properties, so conventional separation methods (such as solvent extraction, ion exchange, precipitation, chemical reduction, etc.) are difficult to effectively apply. They have poor selectivity, low separation efficiency, high consumption of chemical reagents, environmental pollution, high energy consumption, complex processes, and safety issues. Summary of the invention

[0003] In view of this, some embodiments disclose a method for separating similar metal pairs by molten salt electrolysis, comprising:

[0004] A cylindrical inert metal electrode is used as the first cathode; wherein the cylindrical inert metal electrode has a centrally symmetrical internal cavity;

[0005] Using a similar metal pair mixture as the first anode, wherein the similar metal pair mixture consists of a high-activity metal and a low-activity metal, and the content of the low-activity metal is greater than that of the high-activity metal;

[0006] A eutectic sodium potassium salt or a eutectic lithium potassium salt containing a low-activity metal high-valent salt is used as a molten salt electrolyte and placed in the internal volume of the first cathode, and a first anode is arranged at the central axis position of the first cathode, and a first constant current electrolysis is performed under set conditions;

[0007] During the first constant current electrolysis process, a uniform radial electric field is formed between the first anode and the inner surface of the first cathode, and the high-activity metal atoms and the low-activity metal atoms successively enter the molten salt electrolyte in the form of ions, and are further reduced and deposited on the inner wall surface of the cylindrical inert metal electrode in the form of alloys; wherein the ratio of the low-activity metal to the high-activity metal in the alloy is greater than the ratio of the low-activity metal to the high-activity metal in a mixture of similar metal pairs;

[0008] A cylindrical inert metal electrode with an alloy deposited thereon is used as the second anode, and the first anode after the first constant current electrolysis is used as the second cathode. A second constant current electrolysis is carried out under set conditions in the same molten salt electrolyte as the first constant current electrolysis, and the highly active metal dissolves into the molten salt electrolyte to achieve separation of the highly active metal from the low active metal.

[0009] In the method for separating similar metal pairs by molten salt electrolysis disclosed in some embodiments, a first constant current electrolysis and a second constant current electrolysis are performed alternately multiple times.

[0010] In the method for separating similar metal pairs by molten salt electrolysis disclosed in some embodiments, the mass concentration of the high-valent salt of the low-activity metal in the molten salt electrolyte is 1-20%.

[0011] Some embodiments disclose a method for separating similar metal pairs by molten salt electrolysis, wherein the similar metal pair mixture is a zirconium-hafnium mixture, a niobium-tantalum mixture, a tungsten-molybdenum mixture, or a titanium-vanadium mixture.

[0012] Some embodiments disclose a method for separating similar metal pairs by molten salt electrolysis, wherein the low-activity metal high-valent salt is K2ZrF6, K2TaF7, K2MoO4 or K3VO4.

[0013] In some embodiments of the method for separating similar metal pairs by molten salt electrolysis, the eutectic sodium potassium salt is NaCl-KCl; the eutectic lithium potassium salt is LiCl-KCl.

[0014] In some embodiments of the method for separating similar metal pairs by molten salt electrolysis, the current density of the first constant current electrolysis is 0.01 to 10 A·cm -2 .

[0015] In the method for separating similar metal pairs by molten salt electrolysis disclosed in some embodiments, the current density of the second constant current electrolysis is 5 to 50 mA.

[0016] In the method for separating similar metal pairs by molten salt electrolysis disclosed in some embodiments, the electrolysis temperature of the first constant current electrolysis and the electrolysis temperature of the second constant current electrolysis are both set to 450-750°C.

[0017] Some embodiments disclose a device for separating similar metal pairs by molten salt electrolysis, which is used to implement the above-mentioned method for separating similar metal pairs by molten salt electrolysis, including:

[0018] The cylindrical inert metal electrode has a centrally symmetrical internal cavity; the cylindrical inert metal electrode is made of metal nickel or stainless steel;

[0019] The similar metal pair mixture electrode is arranged at the central axis position of the inner cavity of the cylindrical inert metal electrode; the similar metal pair mixture is composed of a high-activity metal and a low-activity metal, and the content of the low-activity metal is greater than that of the high-activity metal;

[0020] The molten salt electrolyte is composed of a eutectic sodium potassium salt or a eutectic lithium potassium salt containing a low-activity metal high-valent salt, and is arranged in the inner cavity of a cylindrical inert metal electrode.

[0021] The device for separating similar metal pairs by molten salt electrolysis disclosed in the embodiment of the present invention, the cylindrical inert metal electrode can effectively expand the electrode surface area, reduce the current density, and even out the current distribution, avoid ion concentration, and facilitate ion migration. It can also make the electrolysis products relatively evenly distributed inside the cylindrical inert metal electrode, avoiding the defects of traditional molten salt electrolysis products falling off the electrode, avoiding multi-layer accumulation, and making it easier for more active impurity metals to dissolve into the molten salt electrolyte. The method for separating similar metal pairs by molten salt electrolysis disclosed in the embodiment of the present invention, according to the electronegativity difference and redox sequence of similar metal pairs, continuously and alternately performs the first constant current electrolysis and the second constant current electrolysis to achieve the separation of similar metal pairs. The process flow is simple, easy to control, easy to operate, and does not produce harmful gases. It has good application prospects in the field of separation and purification of similar metal pairs. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 Schematic diagram of the electrolysis of molten salts to separate similar metal pairs. DETAILED DESCRIPTION

[0023] The word "embodiment" used here as an "exemplary" does not necessarily mean that any embodiment described is superior to or better than other embodiments. Unless otherwise specified, the performance index tests in the embodiments of this application are performed using conventional test methods in the art. It should be understood that the terms described in this application are only used to describe specific implementation methods and are not used to limit the content disclosed in this application.

[0024] Unless otherwise specified, the technical and scientific terms used in this document have the same meanings as commonly understood by ordinary technicians in the technical field to which this application belongs; other experimental methods and technical means not specifically specified in this application refer to experimental methods and technical means commonly used by ordinary technicians in this field.

[0025] The terms "substantially" and "approximately" used herein are used to describe small fluctuations. For example, they can refer to less than or equal to ±5%, such as less than or equal to ±2%, such as less than or equal to ±1%, such as less than or equal to ±0.5%, such as less than or equal to ±0.2%, such as less than or equal to ±0.1%, such as less than or equal to ±0.05%. The numerical data represented or presented in the range format herein are used only for convenience and brevity, and should therefore be flexibly interpreted as including not only the values ​​clearly listed as the limits of the range, but also all independent values ​​or sub-ranges contained in the range. For example, the numerical range of "1-5%" should be interpreted as including not only the clearly listed values ​​of 1% to 5%, but also the independent values ​​and sub-ranges within the range shown. Therefore, independent values ​​such as 2%, 3.5% and 4% and sub-ranges such as 1%-3%, 2%-4% and 3%-5% are included in this numerical range. This principle also applies to the range of only one numerical value. In addition, such an interpretation applies regardless of the width of the range or the characteristics described.

[0026] In this document, including in the claims, transitional words such as "comprises," "includes," "with," "having," "containing," "involving," "accommodating," etc. are understood to be open-ended, i.e., meaning "including but not limited to." Only the transitional words "consisting of" and "composed of" are closed transitional words.

[0027] In order to better illustrate the content of the present application, numerous specific details are provided in the specific examples below. It should be understood by those skilled in the art that the present application can also be implemented without certain specific details. In the embodiments, some methods, means, instruments, equipment, etc. well known to those skilled in the art are not described in detail in order to highlight the main purpose of the present application.

[0028] Under the premise of no conflict, the technical features disclosed in the embodiments of the present application can be arbitrarily combined, and the obtained technical solutions belong to the contents disclosed in the embodiments of the present application. It should be noted that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like mentioned in the present application indicate the orientation or position relationship based on the orientation or position relationship shown in the accompanying drawings, which is only for the convenience of describing the technical features and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation of the present invention, unless it conflicts with the context. In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance, unless it conflicts with the context.

[0029] In some embodiments, a method for separating similar metal pairs by molten salt electrolysis comprises:

[0030] A cylindrical inert metal electrode is used as the first cathode; wherein the cylindrical inert metal electrode has a centrally symmetrical internal cavity; the electrolysis reaction is carried out in the internal cavity of the cylindrical inert metal electrode. Since the internal cavity of the cylindrical inert metal electrode has a large surface area, under the same current, the electrolysis current density on the cylindrical inert metal electrode is smaller than that of a conventional electrode, the current distribution is uniform, and the electric field distribution is uniform, so that when the metal is deposited by the first constant current electrolysis, the product will not be too concentrated. In addition, the difference in electronegativity between the two metals makes the reduced high-activity metal generally adhere to and mix with the outer layer of the low-activity metal, and tends to be distributed in a non-layered manner, so that when the high-activity metal is separated by the second constant current electrolysis, the high-activity metal is easily oxidized and dissolved out of the alloy;

[0031] Using a similar metal pair mixture as the first anode, wherein the similar metal pair mixture consists of a high-activity metal and a low-activity metal, and the content of the low-activity metal is greater than that of the high-activity metal;

[0032] like Figure 1 As shown, a eutectic sodium potassium salt or a eutectic lithium potassium salt containing a low-activity metal high-valent salt is used as a molten salt electrolyte and placed in the internal volume of the first cathode, the first anode is set at the central axis position of the first cathode, the switch 1 is connected, the first anode is connected to the positive electrode of the DC power supply, the first cathode is connected to the negative electrode of the DC power supply, and the first constant current electrolysis is performed under the set conditions;

[0033] During the first constant current electrolysis process, a uniform radial electric field is formed between the first anode and the inner surface of the first cathode. The activity of the highly active metal atoms is stronger than that of the low-active metal atoms, so that the highly active metal atoms and the low-active metal atoms in the similar metal pair mixture enter the molten salt electrolyte in the form of ions one after another. Since the ability of the low-active metal ions to obtain electrons and be reduced to metals is stronger than that of the highly active metal ions, the low-active metal ions in the molten salt electrolyte will preferentially obtain electrons and be reduced to metals, so that the reduction amount of the low-active metal ions is greater than that of the high-active metal ions, and further reduced and deposited on the inner wall surface of the cylindrical inert metal electrode in the form of a low-active metal alloy with a low content of high-active metal; wherein the ratio of the low-active metal to the high-active metal in the alloy is greater than the ratio of the low-active metal to the high-active metal in the similar metal pair mixture;

[0034] The first anode reacts: M i -xe - =M i x+ , M j -xe - =M j x+ ;

[0035] The first cathode reaction: M j x+ +xe - =M j , M i x+ +xe - =M i ;

[0036] Among them, M i M is a highly active metal. j It is a low-activity metal. After the reaction is completed, M j The content is greater than M i Content;

[0037] Disconnect switch 1 and connect switch 2, use the cylindrical inert metal electrode deposited with the alloy as the second anode, and the first anode after the first constant current electrolysis as the second cathode. In the same molten salt electrolyte as the first constant current electrolysis, the second anode is connected to the positive electrode of the DC power supply, and the second cathode is connected to the negative electrode of the DC power supply, and the second constant current electrolysis is performed under the set conditions;

[0038] During the second constant current electrolysis process, the electrolysis current density on the cylindrical inert metal electrode is smaller than that of the conventional electrode, the current distribution is uniform, and the electric field distribution is uniform, so that the highly active metal in the alloy will preferentially dissolve into the molten salt electrolyte. In the alloy, the amount of highly active metal oxidized and dissolved into the molten salt electrolyte is greater than the amount of low-activity metal oxidized and dissolved into the molten salt electrolyte, thereby achieving separation of highly active metals from low-activity metals and reducing the amount of highly active metals in the alloy.

[0039] The second anode reacts: M i -xe - =M i x+ , M j -xe - =M j x+ ;

[0040] The second cathode reacts: M j x+ +xe - =M j , M i x+ +xe - =M i ;

[0041] Among them, M i M is a highly active metal. j It is a low-activity metal. After the reaction is completed, M j The content is greater than M iand the ratio of the low-activity metal to the high-activity metal is greater than the ratio of the low-activity metal to the high-activity metal on the first cathode.

[0042] In some embodiments, the first constant current electrolysis and the second constant current electrolysis are performed alternately for multiple times until the similar metal pairs are completely separated. The first constant current electrolysis realizes the preliminary separation of low-activity metals and high-activity metals, and the second constant current electrolysis realizes the further separation of low-activity metals and high-activity metals. In order to improve the purity of the metals in the separated products, the first constant current electrolysis and the second constant current electrolysis are performed alternately for multiple times, and the low-activity metals and high-activity metals can be completely separated. Generally, a single unidirectional electrolysis has a certain effect on the separation of similar metal pairs. However, taking the separation of zirconium and hafnium as an example, a single unidirectional electrolysis cannot achieve the set purity or impurity removal effect standard, so the electrolysis product is further decontaminated by reverse electrolysis; at the same time, due to the short single cycle time, multiple cycles are required to accumulate the electrolysis products.

[0043] Generally, when the content of high-activity metal element in the second anode electrolysis product is lower than 100 ppm, it can be considered that the second anode electrolysis product is pure low-activity metal, and it can be determined that similar metals in the similar metal pair are completely separated.

[0044] For different similar metal pairs, the electrolysis parameters are set according to the properties of the similar metal pairs and the required purity of the second anode electrolysis product. Generally, the electrolysis voltage and the electrolysis current are set according to the reduction potential difference between the high-activity metal and the low-activity metal, the electrolysis temperature is set according to the melting points of the high-activity metal and the low-activity metal, and the number of cyclic electrolysis is set according to the required purity of the second anode electrolysis product.

[0045] The number of cycles of electrolysis N = (XY) / M;

[0046] Wherein, X is the content of highly active metal elements in the alloy of similar metal pairs, Y is the content of highly active metal elements in the set product, and M is the content of highly active metal elements separated by single cycle electrolysis.

[0047] Generally, the first electrolysis and the second electrolysis are both set as constant current electrolysis. By controlling the electrolysis temperature during the constant current electrolysis process, the ion migration rate in the electrolyte can be controlled, thereby achieving control and regulation of the electrolysis rate.

[0048] In some embodiments, the mass concentration of the low-activity metal high-valent salt in the molten salt electrolyte is 1-20%. For example, when the mass concentration of the low-activity metal high-valent salt is 10%, that is, the low-activity metal high-valent salt is configured in proportion to 10g, and the eutectic sodium potassium salt or eutectic lithium potassium salt is configured in proportion to 90g.

[0049] In some embodiments, the similar metal pair mixture is a zirconium-hafnium mixture, a niobium-tantalum mixture, a tungsten-molybdenum mixture, or a titanium-vanadium mixture.

[0050] In some embodiments, the low-activity high-valent metal salt is K2ZrF6, K2TaF7, K2MoO4 or K3VO4. Generally, K2ZrF6 is used for zirconium and hafnium separation, K2TaF7 is used for niobium and tantalum separation, K2MoO4 is used for tungsten and molybdenum separation, and K3VO4 is used for titanium and vanadium separation.

[0051] In some embodiments, the eutectic sodium potassium salt is NaCl-KCl, and the eutectic lithium potassium salt is LiCl-KCl, wherein the mass ratio of NaCl-KCl is 44:56, and the mass ratio of LiCl-KCl is 45:55.

[0052] In some embodiments, the electrolysis temperature of the first constant current electrolysis is set to 450-750°C.

[0053] In some embodiments, the current density of the first constant current electrolysis is 0.01 to 10 A·cm -2 .

[0054] In some embodiments, the electrolysis temperature of the second constant current electrolysis is set to 450-750°C.

[0055] In some embodiments, the current density of the second constant current electrolysis is 5 to 50 mA. Compared with the current density of the first constant current electrolysis, the current density of the second constant current electrolysis is smaller because the purpose of the second constant current electrolysis is mainly to remove the high-activity metal mixed with the low-activity metal and improve the purity of the low-activity metal; at a lower current density, the more active high-activity metal will dissolve, but the less active low-activity metal will not dissolve, therefore, the current density of the second constant current electrolysis is set lower than the current density of the first constant current electrolysis.

[0056] In some embodiments, the device for separating similar metal pairs by molten salt electrolysis is used to implement the above-mentioned method for separating similar metal pairs by molten salt electrolysis, comprising:

[0057] The cylindrical inert metal electrode has a centrally symmetrical internal cavity; the electrolysis reaction is carried out in the internal cavity of the cylindrical inert metal electrode. The cylindrical symmetrical structure can effectively expand the electrode surface area, reduce the current density, and even out the current distribution, thereby avoiding ion concentration and facilitating ion migration, so that the electrolysis products are relatively evenly distributed in the internal cavity of the cylindrical inert metal electrode, and can also avoid the defect of the traditional molten salt electrolysis products falling off the electrode;

[0058] The cylindrical inert metal electrode is made of nickel or stainless steel. Nickel and stainless steel have good corrosion resistance, can remain stable in strong acidic or alkaline electrolytes, have good conductivity, can effectively transmit current, ensure the efficient electrolysis process, are not easy to deform or damage, and are not easy to react with electrolytes, which is conducive to improving electrolysis efficiency or preventing the occurrence of certain side reactions;

[0059] The similar metal pair mixture electrode is arranged at the central axis position of the internal cavity of the cylindrical inert metal electrode, so that a uniform radial electric field can be formed between the similar metal pair mixture electrode and the inner surface of the cylindrical inert metal electrode, which is beneficial to ion migration; the similar metal pair mixture is composed of a high-activity metal and a low-activity metal, and the content of the low-activity metal is greater than that of the high-activity metal;

[0060] The molten salt electrolyte is composed of a eutectic sodium potassium salt or a eutectic lithium potassium salt containing a low-activity metal high-valent salt, and is arranged in the inner cavity of a cylindrical inert metal electrode.

[0061] The technical details are further illustrated below in conjunction with embodiments.

[0062] Example 1

[0063] Example 1 discloses a method for separating zirconium and hafnium by molten salt electrolysis, comprising:

[0064] A cylindrical metal nickel electrode is used as the first cathode; wherein the cylindrical metal nickel electrode has a centrally symmetrical internal cavity;

[0065] A zirconium-hafnium mixture is used as a first anode, wherein the zirconium-hafnium mixture consists of hafnium and zirconium, and the content of zirconium is greater than that of hafnium;

[0066] A eutectic sodium potassium salt containing 10 wt% K2ZrF6 was used as a molten salt electrolyte and placed in the inner cavity of the first cathode. The first anode was set at the central axis of the first cathode. The electrolysis temperature was 750 ° C and the current density was 0.1 A cm -2 Under the condition of , the first constant current electrolysis is carried out;

[0067] During the first constant current electrolysis process, a uniform radial electric field is formed between the first anode and the inner surface of the first cathode, and hafnium and zirconium successively enter the molten salt electrolyte in the form of ions, and are further reduced and deposited on the inner wall surface of the cylindrical metal nickel electrode in the form of an alloy; wherein the ratio of zirconium to hafnium in the alloy is greater than the ratio of zirconium to hafnium in the zirconium-hafnium mixture;

[0068] A cylindrical nickel electrode with alloy deposited thereon is used as the second anode, and the first anode after the first constant current electrolysis is used as the second cathode. In the same molten salt electrolyte as the first constant current electrolysis, a second constant current electrolysis is performed at a current density of 10 mA, and hafnium is dissolved into the molten salt electrolyte.

[0069] The first constant current electrolysis and the second constant current electrolysis are performed alternately to separate hafnium from zirconium to obtain a zirconium alloy, wherein the hafnium content in the zirconium alloy is 0.05%.

[0070] Example 2

[0071] Example 2 discloses a method for separating niobium and tantalum by molten salt electrolysis, comprising:

[0072] A cylindrical metal nickel electrode is used as the first cathode; wherein the cylindrical metal nickel electrode has a centrally symmetrical internal cavity;

[0073] A niobium-tantalum mixture is used as the first anode, wherein the niobium-tantalum mixture consists of niobium and tantalum, and the content of tantalum is greater than that of niobium;

[0074] A eutectic sodium potassium salt containing 10 wt% K2TaF7 was used as a molten salt electrolyte and placed in the inner cavity of the first cathode. The first anode was set at the central axis of the first cathode. The electrolysis temperature was 750 ° C and the current density was 0.1 A cm -2 Under the condition of , the first constant current electrolysis is carried out;

[0075] During the first constant current electrolysis process, a uniform radial electric field is formed between the first anode and the inner surface of the first cathode, and niobium and tantalum enter the molten salt electrolyte in the form of ions, and are further reduced and deposited on the inner wall surface of the cylindrical metal nickel electrode in the form of alloy; wherein the ratio of tantalum to niobium in the alloy is greater than the ratio of tantalum to niobium in the niobium-tantalum mixture;

[0076] A cylindrical nickel electrode with alloy deposited thereon is used as the second anode, and the first anode after the first constant current electrolysis is used as the second cathode. In the same molten salt electrolyte as the first constant current electrolysis, a second constant current electrolysis is performed at a current density of 10 mA, and niobium is dissolved into the molten salt electrolyte.

[0077] The first constant current electrolysis and the second constant current electrolysis are performed alternately to separate niobium from tantalum to obtain a tantalum alloy, wherein the niobium content in the tantalum alloy is 0.046%.

[0078] Example 3

[0079] Example 3 discloses a method for separating vanadium and titanium by molten salt electrolysis, comprising:

[0080] A cylindrical metal nickel electrode is used as the first cathode; wherein the cylindrical metal nickel electrode has a centrally symmetrical internal cavity;

[0081] A vanadium-titanium mixture is used as the first anode, wherein the vanadium-titanium mixture consists of vanadium and titanium, and the content of vanadium is greater than that of titanium;

[0082] A eutectic sodium potassium salt containing 10 wt% K3VO4 was used as a molten salt electrolyte and placed in the inner cavity of the first cathode. The first anode was set at the central axis of the first cathode. The electrolysis temperature was 750 ° C and the current density was 0.1 A cm -2 Under the condition of , the first constant current electrolysis is carried out;

[0083] During the first constant current electrolysis process, a uniform radial electric field is formed between the first anode and the inner surface of the first cathode, and titanium and vanadium successively enter the molten salt electrolyte in the form of ions, and are further reduced and deposited on the inner wall surface of the cylindrical metal nickel electrode in the form of alloys; wherein the ratio of vanadium to titanium in the alloy is greater than the ratio of vanadium to titanium in the titanium-vanadium mixture;

[0084] A cylindrical metal nickel electrode deposited with an alloy is used as the second anode, and the first anode after the first constant current electrolysis is used as the second cathode. In the same molten salt electrolyte as the first constant current electrolysis, a second constant current electrolysis is performed at a current density of 10 mA, and titanium is dissolved into the molten salt electrolyte.

[0085] The first constant current electrolysis and the second constant current electrolysis are performed alternately to separate titanium from vanadium and obtain a vanadium alloy, wherein the titanium content in the vanadium alloy is 0.045%.

[0086] Example 4

[0087] Example 4 discloses a method for separating zirconium and hafnium by molten salt electrolysis, comprising:

[0088] A cylindrical stainless steel electrode is used as the first cathode; wherein the cylindrical stainless steel electrode has a centrally symmetrical internal cavity;

[0089] A zirconium-hafnium mixture is used as a first anode, wherein the zirconium-hafnium mixture consists of hafnium and zirconium, and the content of zirconium is greater than that of hafnium;

[0090] A eutectic sodium potassium salt containing 10 wt% K2ZrF6 was used as a molten salt electrolyte and placed in the inner cavity of the first cathode. The first anode was set at the central axis of the first cathode. The electrolysis temperature was 750 ° C and the current density was 0.1 A cm -2 Under the condition of , the first constant current electrolysis is carried out;

[0091] During the first constant current electrolysis process, a uniform radial electric field is formed between the first anode and the inner surface of the first cathode, and hafnium and zirconium successively enter the molten salt electrolyte in the form of ions, and are further reduced and deposited on the inner wall surface of the cylindrical stainless steel electrode in the form of alloys; wherein the ratio of zirconium to hafnium in the alloy is greater than the ratio of zirconium to hafnium in the zirconium-hafnium mixture;

[0092] The cylindrical stainless steel electrode on which the alloy is deposited is used as the second anode, and the first anode after the first constant current electrolysis is used as the second cathode. In the same molten salt electrolyte as the first constant current electrolysis, a second constant current electrolysis is performed at a current density of 10 mA, and hafnium is dissolved into the molten salt electrolyte.

[0093] The first constant current electrolysis and the second constant current electrolysis are performed alternately to separate hafnium from zirconium to obtain a zirconium alloy, wherein the hafnium content in the zirconium alloy is 0.03%.

[0094] Example 5

[0095] Example 5 discloses a method for separating niobium and tantalum by molten salt electrolysis, comprising:

[0096] A cylindrical stainless steel electrode is used as the first cathode; wherein the cylindrical stainless steel electrode has a centrally symmetrical internal cavity;

[0097] A niobium-tantalum mixture is used as the first anode, wherein the niobium-tantalum mixture consists of niobium and tantalum, and the content of tantalum is greater than that of niobium;

[0098] A eutectic sodium potassium salt containing 10 wt% K2TaF7 was used as a molten salt electrolyte and placed in the inner cavity of the first cathode. The first anode was set at the central axis of the first cathode. The electrolysis temperature was 750 ° C and the current density was 0.1 A cm -2 Under the condition of , the first constant current electrolysis is carried out;

[0099] During the first constant current electrolysis process, a uniform radial electric field is formed between the first anode and the inner surface of the first cathode, and niobium and tantalum enter the molten salt electrolyte in the form of ions, and are further reduced and deposited on the inner wall surface of the cylindrical stainless steel electrode in the form of alloys; wherein the ratio of tantalum to niobium in the alloy is greater than the ratio of tantalum to niobium in the niobium-tantalum mixture;

[0100] The cylindrical stainless steel electrode on which the alloy is deposited is used as the second anode, and the first anode after the first constant current electrolysis is used as the second cathode. In the same molten salt electrolyte as the first constant current electrolysis, the second constant current electrolysis is carried out at a current density of 10 mA, and niobium is dissolved into the molten salt electrolyte.

[0101] The first constant current electrolysis and the second constant current electrolysis are performed alternately to separate niobium and tantalum to obtain a tantalum alloy, wherein the niobium content in the tantalum alloy is 0.025%.

[0102] The device for separating similar metal pairs by molten salt electrolysis disclosed in the embodiment of the present invention, the cylindrical inert metal electrode can effectively expand the electrode surface area, reduce the current density, and even out the current distribution, avoid ion concentration, and facilitate ion migration. It can also make the electrolysis products relatively evenly distributed inside the cylindrical inert metal electrode, avoiding the defects of traditional molten salt electrolysis products falling off the electrode, avoiding multi-layer accumulation, and making it easier for more active impurity metals to dissolve into the molten salt electrolyte. The method for separating similar metal pairs by molten salt electrolysis disclosed in the embodiment of the present invention, according to the electronegativity difference and redox sequence of similar metal pairs, continuously and alternately performs the first constant current electrolysis and the second constant current electrolysis to achieve the separation of similar metal pairs. The process flow is simple, easy to control, easy to operate, and does not produce harmful gases. It has good application prospects in the field of separation and purification of similar metal pairs.

[0103] The technical solutions disclosed in the present invention and the technical details disclosed in the embodiments are merely illustrative of the inventive concept of the present invention and do not constitute a limitation on the technical solutions of the present invention. Any conventional changes, substitutions or combinations of the technical details disclosed in the embodiments of the present invention have the same inventive concept as the present invention and are within the protection scope of the claims of the present invention.

Claims

1. A method for separating similar metal pairs by molten salt electrolysis, characterized in that: include: A cylindrical inert metal electrode is used as the first cathode; wherein the cylindrical inert metal electrode has a centrally symmetrical internal cavity; Using a similar metal pair mixture as the first anode, wherein the similar metal pair mixture consists of a high-activity metal and a low-activity metal, and the content of the low-activity metal is greater than that of the high-activity metal; A eutectic sodium potassium salt or a eutectic lithium potassium salt containing a low-activity metal high-valent salt is used as a molten salt electrolyte and placed in the internal volume of the first cathode, and a first anode is arranged at the central axis position of the first cathode, and a first constant current electrolysis is performed under set conditions; During the first constant current electrolysis process, a uniform radial electric field is formed between the first anode and the inner surface of the first cathode, and the high-activity metal atoms and the low-activity metal atoms successively enter the molten salt electrolyte in the form of ions, and are further reduced and deposited on the inner wall surface of the cylindrical inert metal electrode in the form of alloys; wherein the ratio of the low-activity metal to the high-activity metal in the alloy is greater than the ratio of the low-activity metal to the high-activity metal in a mixture of similar metal pairs; A cylindrical inert metal electrode with an alloy deposited thereon is used as the second anode, and the first anode after the first constant current electrolysis is used as the second cathode. A second constant current electrolysis is carried out under set conditions in the same molten salt electrolyte as the first constant current electrolysis, and the highly active metal dissolves into the molten salt electrolyte to achieve separation of the highly active metal from the low active metal.

2. The method for separating similar metal pairs by molten salt electrolysis according to claim 1, characterized in that: The first constant current electrolysis and the second constant current electrolysis are performed alternately multiple times.

3. The method for separating similar metal pairs by molten salt electrolysis according to claim 1, characterized in that: In the molten salt electrolyte, the mass concentration of the low-activity metal high-valence salt is 1 to 20%.

4. The method for separating similar metal pairs by molten salt electrolysis according to claim 1, characterized in that: The similar metal pair mixture is a zirconium-hafnium mixture, a niobium-tantalum mixture, a tungsten-molybdenum mixture or a titanium-vanadium mixture.

5. The method for separating similar metal pairs by molten salt electrolysis according to claim 1, characterized in that: The low-activity high-valent metal salt is K2ZrF6, K2TaF7, K2MoO4 or K3VO4.

6. The method for separating similar metal pairs by molten salt electrolysis according to claim 1, characterized in that: The eutectic sodium potassium salt is NaCl-KCl; the eutectic lithium potassium salt is LiCl-KCl.

7. The method for separating similar metal pairs by molten salt electrolysis according to claim 1, characterized in that: The current density of the first constant current electrolysis is 0.01 to 10 A·cm -2 .

8. The method for separating similar metal pairs by molten salt electrolysis according to claim 1, characterized in that: The current density of the second constant current electrolysis is 5-50 mA.

9. The method for separating similar metal pairs by molten salt electrolysis according to claim 1, characterized in that: The electrolysis temperature of the first constant current electrolysis and the electrolysis temperature of the second constant current electrolysis are both set to 450-750°C.

10. A device for separating similar metal pairs by molten salt electrolysis, used to implement the method for separating similar metal pairs by molten salt electrolysis as claimed in any one of claims 1 to 9, characterized in that: include: A cylindrical inert metal electrode having a centrally symmetrical internal cavity; The cylindrical inert metal electrode is made of nickel or stainless steel; A similar metal pair mixture electrode is arranged at the central axis position of the inner cavity of the cylindrical inert metal electrode; the similar metal pair mixture is composed of a high-activity metal and a low-activity metal, and the content of the low-activity metal is greater than that of the high-activity metal; The molten salt electrolyte is composed of a eutectic sodium potassium salt or a eutectic lithium potassium salt containing a low-activity metal high-valent salt, and is arranged in the inner cavity of a cylindrical inert metal electrode.

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