Metal electrochemical dissolution method based on ionic liquid medium

Abstract

The invention discloses a metal electrochemical dissolution method based on an ionic liquid medium. The method comprises the following steps: 1, preparing a K < + >-containing reagent, and mutually dissolving the K < + >-containing reagent with the ionic liquid BMImNTf2; 2, removing water from the ionic liquid and keeping a water-free environment; step 3, electrochemically dissolving the target metal; the problems that a traditional organic acid dissolving method is small in dissolving amount, harsh in experiment condition, long in consumed time and the like are solved, the metal ion concentration in the prepared ionic liquid is close to 30 g / L, and the metal ion concentration requirement for electrolytic refining cathode dendritic crystal growth is met. And meanwhile, impurities influencing electrolytic refining are not introduced, and the method can be used for introducing most of metal capable of being oxidized and dissolved and has wide applicability to similar requirements.

Description

Technical Field

[0001] This patent relates to the field of molten salt electrolytic refining technology, and specifically to a metal electrochemical dissolution method based on ionic liquid medium. Background Art

[0002] When using ionic liquid (room temperature molten salt: BMImNTf2) as an electrolyte for electrolytic refining and purification of metals, it is necessary to prepare ionic liquid containing target metal ions to start the continuous electrolytic refining process. At the same time, in order to meet the purity requirements of metal products, the valence state of the metal ions in the ionic liquid needs to remain stable and the reduction potential should not exceed the electrochemical window of the dielectric.

[0003] Therefore, it is necessary to develop a metal electrochemical dissolution method based on ionic liquid medium, which can dissolve the metal in the ionic liquid in an ionic state by adjusting specific process parameters. At the same time, the valence state of the metal ions can be kept stable and meet the reduction deposition requirements by controlling electrical parameters and environment. Summary of the invention

[0004] The object of the present invention is to provide a method for electrochemical dissolution of metals based on ionic liquid media to achieve the preparation of ionic liquids containing target metal ions while meeting the requirements for molten salt for electrolytic refining, which are:

[0005] (1) The metal ion concentration meets the standard;

[0006] (2) The valence state of metal ions is single and stable;

[0007] (3) The reduction potential of the metal ions does not exceed the electrochemical window of the ionic liquid medium.

[0008] The technical solution of the present invention is as follows: A method for electrochemical dissolution of metal based on ionic liquid medium, comprising the following steps;

[0009] Step 1: Prepare K-containing + Reagents, and miscible with ionic liquid BMImNTf2;

[0010] Step 2: Remove water from the ionic liquid and maintain an anhydrous environment;

[0011] Step 3: electrochemical dissolution of the target metal;

[0012] Step 3.1: Use the target metal as the working electrode, the molybdenum rod as the counter electrode, and Ag / AgCl as the reference electrode;

[0013] Step 3.2: Start electrochemical dissolution;

[0014] Step 3.3: During the electrochemical dissolution process, H2 continues to emerge at the counter electrode (3), the target metal continues to dissolve at the working electrode, and the ionic liquid BMImNTf2 gradually turns red. The electrolysis is stopped when the target metal is deposited on the counter electrode.

[0015] In the step 1, KOH and excess HNTf2 are reacted to prepare a K-containing + Reagents.

[0016] In the step 1, K + During the mixing process of the reagent and the ionic liquid BMImNTf2, stirring was maintained at 50°C.

[0017] In the step 2, the ionic liquid is transferred to an atmosphere glove box after dehydration, and the atmosphere is maintained at 0.1 ppm water and 0.1 ppm oxygen.

[0018] In the step 3.1, the target metal is uranium metal in the form of ribbons or chips.

[0019] In step 3.1, the target metal is wrapped in a molybdenum mesh and tied to a molybdenum rod as a working electrode.

[0020] In step 3.1, the three electrodes are clamped by the plastic cover plate and are kept from touching the bottom and the wall.

[0021] In step 3.1, an electrochemical workstation was used to set the working electrode to a constant potential of 1.2V.

[0022] In step 3.3, the solution is kept acidic until the rate of H2 evolution decreases and the target metal is deposited on the molybdenum rod of the counter electrode, and then the electrolysis is stopped.

[0023] The method also includes step 4: taking out the working electrode, the reference electrode, and the counter electrode, and detecting the content of the target metal ions in the ionic liquid after electrochemical dissolution.

[0024] The remarkable effects of the present invention are:

[0025] (1) The present invention develops a method for preparing ionic liquids containing target metal ions, which solves the problems of small dissolution volume, harsh experimental conditions, and long time consumption in traditional organic acid dissolution methods. The metal ion concentration in the prepared ionic liquid is close to 30g / L, which meets the metal ion concentration requirement for cathode dendrite growth in electrolytic refining.

[0026] (2) The present invention adopts an electrochemical dissolution method to solve the problem that the organic cluster components in the ionic liquid structure are difficult to dissolve with most metal compounds, while not introducing impurities that affect electrolytic refining. In addition, this method can be used to introduce most oxidizable and soluble metals, and has broad applicability to similar needs.

[0027] (3) The present invention uses ionic liquid as the electrolyte for electrolytic refining. Ionic liquid has the characteristics of room temperature molten salt state, extremely low vapor pressure, thermal stability, radiation stability, wide chemical window, etc. Compared with traditional high-temperature molten salt, it can reduce the corrosion of volatile salt to equipment, reduce the difficulty of electrolytic refining operation, and the electrolytic reaction can be observed in real time intuitively, thereby reducing energy consumption. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Attached Figure 1 A schematic diagram of a three-electrode system is shown for the use scenario of the present invention;

[0029] Attached Figure 2 Schematic diagram of the transformation of ionic liquid to red;

[0030] In the figure: 1 working electrode (anode), 2 reference electrode, 3 counter electrode (cathode), 4 target metal, 5 H2, 7 target metal deposition DETAILED DESCRIPTION

[0031] Many specific details are described in the following description to facilitate a full understanding of the present application. However, the present application can be implemented in many other ways than those described herein, and those skilled in the art can make similar generalizations without violating the connotation of the present application, so the present application is not limited by the specific implementation disclosed below.

[0032] The terms used in one or more embodiments of the present application are only for the purpose of describing specific embodiments, and are not intended to limit one or more embodiments of the present application. The singular forms of "a", "said" and "the" used in one or more embodiments of the present application and the appended claims are also intended to include plural forms, unless the context clearly indicates other meanings. It should also be understood that the term "and / or" used in one or more embodiments of the present application refers to and includes any or all possible combinations of one or more associated listed items.

[0033] It should be understood that, although the terms first, second, etc. may be used to describe various information in one or more embodiments of the present application, such information should not be limited to these terms. These terms are only used to distinguish the same type of information from each other. For example, without departing from the scope of one or more embodiments of the present application, the first may also be referred to as the second, and similarly, the second may also be referred to as the first.

[0034] A metal electrochemical dissolution method based on an ionic liquid medium, the method using raw metal and ionic liquid, the method comprising the following steps:

[0035] Step 1: Improve the conductivity of ionic liquids through special formulation;

[0036] Step 2: Remove water from the ionic liquid and maintain an anhydrous environment;

[0037] Step 3: Electrochemical dissolution of target metal.

[0038] Step 4: Take out the working electrode 1, the reference electrode 2, and the counter electrode 3, and detect the content of the target metal deposition 7 on the counter electrode 3.

[0039] Further, in step 1, a K-containing + The reagents react with acid and base (KOH and excess HNTf2) to produce water as a byproduct without introducing other impurities.

[0040] Further, in step 1, the K-containing + The reagent is directly miscible with the ionic liquid (BMImNTf2). BMImNTf2 is 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)immonium salt;

[0041] Furthermore, in step 1, K + During the mixing process of the reagent and the ionic liquid, stirring was maintained at 50°C to prevent flocculation of organic matter.

[0042] Furthermore, in step 2, the ionic liquid is dehydrated by using a vacuum drying oven at 0.1 kPa and 200° C. for 3 hours.

[0043] Furthermore, in step 2, the ionic liquid is transferred to an atmosphere glove box after dehydration, and the atmosphere is maintained at 0.1 ppm water and 0.1 ppm oxygen.

[0044] Furthermore, in step three, the target metal state is in a strip or crumb state to increase the specific surface area.

[0045] Furthermore, in step three, a three-electrode system is used, with the target metal as the anode 1 , the molybdenum rod as the cathode 3 , and Ag / AgCl as the reference electrode 2 .

[0046] Furthermore, in step three, an electrochemical workstation was used to set the anode 1 to a constant potential of 1.2V.

[0047] Furthermore, in step three, the solution is kept acidic, H2 is produced at the cathode, and the anode metal is dissolved and maintains a stable valence state.

[0048] Further, in step 3, H + After exhaustion, metal precipitation occurs at cathode 3, and the metal ion concentration in the ionic liquid has reached the target value.

[0049] Furthermore, in step three, the concentration of metal ions in the ionic liquid is directly related to the amount of excess HNTf2 introduced.

[0050] The following examples are used to clearly and completely describe the technical solutions in the embodiments of the present invention. The embodiments use ionic liquid (BMImNTf2), HNTf2, KOH, and metal chips. The detailed implementation steps of the technical method are as follows:

[0051] Step 1.1: Weigh 20 g of HNTf2, 2 g of KOH, 5 g of uranium metal chips, 30 mL of BMImNTf2, and prepare a 50 mL beaker, molybdenum rod, molybdenum mesh, Ag / AgCl reference electrode, glass rod, oil bath, etc.

[0052] Step 1.2: Place KOH in a beaker and use a burette to add as little water as possible to completely dissolve it. Then pour excess HNTf2 into the beaker, add as little water as possible and use a glass rod to stir continuously until the mixture is completely dissolved and turns yellow and transparent. At this time, the KOH and HNTf2 in the solution are neutralized and remain acidic (pH≈3).

[0053] Step 1.3: Mix the ionic liquid (BMImNTf2) with the prepared K + The solution was mixed and the whole was placed in an oil bath at 50°C and stirred to dissolve the OH - The flocculants produced by combining with organic cations are removed from the beaker and transferred to a vacuum drying oven when the ionic liquid becomes yellow and transparent.

[0054] Step 2: Set a vacuum drying oven at 0.1 kPa and 200° C. to dry the ionic liquid for 3 hours. After that, take out the beaker and transfer it to an atmosphere glove box, maintaining the atmosphere water at 0.1 ppm and oxygen at 0.1 ppm.

[0055] Step 3.1: Wrap the uranium metal chips in a molybdenum mesh and tie it to a molybdenum rod as the working electrode 1 of the three-electrode system. Use another molybdenum rod as the counter electrode 3 and Ag / AgCl as the reference electrode 2. Clamp the three electrodes with a plastic cover and keep the electrodes from touching the bottom or the wall.

[0056] Step 3.2: Connect the electrochemical workstation wire, start the electrochemical test software, set the working electrode potential to 1.2 V, the electrolysis time to 1 hour, and start electrochemical dissolution.

[0057] Step 3.3: During the electrochemical dissolution process, H25 continued to emerge from the counter electrode 3, the shavings of metal 4 continued to dissolve at the working electrode 1, and the ionic liquid gradually turned red. At the same time, the test software interface was observed. The current was maintained at 10 -2 A and continues to increase to 10 -1 A. Electrolysis is stopped when the H2 evolution rate gradually decreases and the target metal deposition 7 appears on the counter electrode molybdenum rod 3.

[0058] Step 4: Take out the working electrode 1, the reference electrode 2, and the counter electrode 3, and use a burette to sample 5 mL for uranium content detection. The result is 29.74 g / L. The uranium concentration in the ionic liquid meets the requirements of electrolytic refining, and a batch of uranium-containing ionic liquid is prepared.

[0059] Step 5: Conduct electrochemical dissolution experiments on different ratios of BMImNTf2, HNTf2, KOH and other reagents. The following results are given: BMImNTf2 30mL, HNTf2 5g, KOH 0.5g, under the same electrolysis conditions, the uranium content is 9.3g / L; BMImNTf230mL, HNTf2 10g, KOH 1g, under the same electrolysis conditions, the uranium content is 19g / L; BMImNTf2 30mL, HNTf2 30g, KOH5g, under the same electrolysis conditions, the ionic liquid deteriorates and does not meet the target requirements. The reagent ratio should be strictly controlled, and the dissolution potential can be appropriately increased.

[0060] The above description is only a preferred embodiment of this patent and is not intended to limit this patent. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of this patent should be included in the scope of protection of this patent.

[0061] It should be noted that, for the above-mentioned method embodiments, for the sake of simplicity of description, they are all expressed as a series of action combinations, but those skilled in the art should be aware that the present application is not limited by the described action sequence, because according to the present application, certain steps can be performed in other sequences or simultaneously. Secondly, those skilled in the art should also be aware that the embodiments described in the specification are all preferred embodiments, and the actions and modules involved are not necessarily required by the present application.

[0062] In the above embodiments, the description of each embodiment has its own emphasis. For parts that are not described in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0063] The preferred embodiments of the present application disclosed above are only used to help explain the present application. The optional embodiments do not describe all the details in detail, nor do they limit the invention to the specific implementation methods described. Obviously, many modifications and changes can be made according to the content of the present application. The present application selects and specifically describes these embodiments in order to better explain the principles and practical applications of the present application, so that those skilled in the art can understand and use the present application well.

Claims

1. A method for electrochemical dissolution of metals based on ionic liquid medium, characterized in that: The steps include: Step 1: Prepare K-containing + Reagents, and miscible with ionic liquid BMImNTf2; Step 2: Remove water from the ionic liquid and maintain an anhydrous environment; Step 3: electrochemical dissolution of the target metal; Step 3.1: Use the target metal (4) as the working electrode (1), a molybdenum rod as the counter electrode (3), and Ag / AgCl as the reference electrode (2); Step 3.2: Start electrochemical dissolution; Step 3.3: During the electrochemical dissolution process, H2 (5) continues to emerge at the counter electrode (3), the target metal (4) continues to dissolve at the working electrode (1), and the ionic liquid BMImNTf2 gradually turns red. The electrolysis is stopped when the target metal deposition (7) appears on the counter electrode (3).

2. The method for electrochemical dissolution of metals based on ionic liquid medium according to claim 1, characterized in that: In the step 1, KOH and excess HNTf2 are reacted to prepare a K-containing + Reagents.

3. The method for electrochemical dissolution of metals based on ionic liquid medium according to claim 1, characterized in that: In the step 1, K + During the mixing process of the reagent and the ionic liquid BMImNTf2, stirring was maintained at 50°C.

4. The method for electrochemical dissolution of metals based on ionic liquid medium according to claim 1, characterized in that: In the step 2, the ionic liquid is transferred to an atmosphere glove box after dehydration, and the atmosphere is maintained at 0.1 ppm water and 0.1 ppm oxygen.

5. The method for electrochemical dissolution of metals based on ionic liquid medium according to claim 1, characterized in that: In the step 3.1, the target metal (4) is uranium metal in the form of ribbons or chips.

6. The method for electrochemical dissolution of metals based on ionic liquid medium according to claim 1, characterized in that: In step 3.1, the target metal (4) is wrapped in a molybdenum mesh and tied to a molybdenum rod as a working electrode (1).

7. The method for electrochemical dissolution of metals based on ionic liquid medium according to claim 1, characterized in that: In step 3.1, the three electrodes are clamped by the plastic cover plate and are kept from touching the bottom and the wall.

8. The method for electrochemical dissolution of metals based on ionic liquid medium according to claim 1, characterized in that: In step 3.1, an electrochemical workstation is used to set the working electrode (1) to a constant potential of 1.2V.

9. The method for electrochemical dissolution of metals based on ionic liquid medium according to claim 1, characterized in that: In the step 3.3, the solution is kept acidic until the rate of H2 (5) evolution decreases and the target metal deposition (7) appears on the counter electrode molybdenum rod (3), and then the electrolysis is stopped.

10. The method for electrochemical dissolution of metals based on ionic liquid medium according to claim 1, characterized in that: The method also includes step 4: taking out the working electrode (1), the reference electrode (2), and the counter electrode (3), and detecting the content of the target metal ions in the ionic liquid after electrochemical dissolution.

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