CN116856010A - Electrochemical recovery method for waste beryllium - Google Patents

Abstract

The invention discloses a method for electrochemical recovery of waste beryllium. The technical solution is to first construct a beryllium-containing fluoride or beryllium-containing fluorochloride molten salt system, and then use waste beryllium as an anode to perform electrochemical selection under a protective gas atmosphere. Through sexual dissolution and deposition, the cathode product is obtained, and finally the salt contained in the cathode product is removed to obtain high-purity metal beryllium. Compared with fire method remelting, etc., the electrochemical reaction recovery of the present invention has a large reaction driving force and can break bonds with large bond energy such as Be-O in waste beryllium, solving the problem of fire method being difficult to remelt. At the same time, electrochemical The recycling control accuracy is high. This application adds beryllium ions to the molten salt system and controls the beryllium salt concentration to keep the beryllium ion concentration relatively stable during the electrochemical process, which facilitates stable electrolysis. If there are no beryllium ions initially, it will be difficult to deposit beryllium on the cathode. The invention realizes the reuse of waste beryllium, which not only makes the waste beryllium harmless, but also realizes its resource utilization, generates economic benefits and at the same time makes up for the shortage of beryllium resources in my country.

Description

A method for electrochemical recycling of waste beryllium

Technical field

The invention relates to a method for electrochemical recovery of waste beryllium and belongs to the technical field of beryllium metallurgy and resource recycling.

Background technique

Metal beryllium has the disadvantage of being too brittle and resulting in poor processing performance. In the production process from metal beryllium to beryllium parts, it is inevitable to produce some scrap beryllium that cannot be put into use. In addition, there are some beryllium parts that have expired. If these waste beryllium can be recycled as secondary resources through electrolytic refining, it will produce huge economic benefits.

Leading U.S. beryllium producer Materion has established a comprehensive recycling program for all of its beryllium products, recycling approximately 40% of the beryllium in new and used beryllium alloy scrap. The following difficulties exist in the recycling of scrap beryllium: (1) As the service life of beryllium products prolongs, beryllium oxide films will be produced. Due to the denseness and large Be-O bond energy, scrap beryllium does not melt at the beryllium bead smelting temperature and is difficult to pass through. Smelting and reuse; (2) The processing of beryllium parts will cause impurity elements to accumulate and migrate into the crystal lattice, making them difficult to remove through smelting. Patent CN115786982 A discloses a method for purifying beryllium waste based on molten salt electrolytic refining. The method emphasizes that the form of waste raw materials must be granular and is loaded into a titanium basket. However, due to the similar potentials of titanium and beryllium, titanium will It is present in recycled products as impurities and is difficult to remove.

Contents of the invention

In view of the shortcomings of the existing technology, the purpose of the present invention is to provide a method for the electrochemical recovery of waste beryllium, which aims to use waste beryllium as raw material to electrochemically selectively recover beryllium and realize high-value recovery of waste beryllium.

In order to achieve the above objects, the technical solution of the present invention is:

A method for electrochemical recycling of waste beryllium, including the following steps:

(1) Construct a beryllium-containing fluoride or beryllium-containing fluorochloride molten salt system;

(2) Using waste beryllium as an anode, perform electrochemical selective dissolution and deposition under a protective gas atmosphere to obtain a cathode product;

(3) Remove the salts contained in the cathode product to obtain high-purity metal beryllium.

Further, the beryllium-containing fluoride molten salt system is _BeF2 - _MFn , and the beryllium-containing fluorochloride molten salt system is _BeF2 - _MFn - _MCln , where _MFn is an alkali metal fluoride other than _BeF2 or One or more types of alkaline earth metal fluorides, MCl _n is one or more types of alkali metal chlorides or alkaline earth metal chlorides.

Further, the BeF ₂ accounts for 10-80 at.% of the BeF ₂ -MF _n or BeF ₂ -MF _n -MCl _n molten salt system.

Further, the MF _n is LiF, NaF, KF, MgF ₂ , CaF ₂ , and BaF ₂ , and the MCl _n is LiCl, NaCl, KCl, BeCl ₂ , MgCl ₂ , CaCl ₂ , and BaCl ₂ .

Further, the waste beryllium is leftover materials produced during beryllium ingot casting and profile processing (such as the outer skin of the ingot and the removed ingot tip, waste chips, and waste powder); defective products in the production of beryllium materials (such as scrapped finished products); One or more types of beryllium parts that have expired. According to the actual situation, the scrap beryllium can be pressed into a certain shape and can be used as an anode.

Further, the protective gas is one of helium, argon, and neon.

Furthermore, the temperature of the electrochemical reaction is 400-1000°C; driven by constant current electricity, the cathode current density of the electrochemical reaction is 0.01-3.0A/cm ² . Preferably, the temperature of the electrochemical reaction is 400-950°C, and the cathode current density is 0.1-1.3A/cm ² .

Furthermore, a pre-reaction is carried out before electrochemistry, the temperature is 400-1000°C, the voltage is 2.0-3.0V, the time is 0.1-2h, and the cathode is replaced after the pre-reaction. Preferably, the pre-reaction temperature is 400-950°C and the time is 0.5-2h.

Furthermore, the cathode material used in the electrochemical reaction is one of high-purity metals, high-entropy alloys, titanium boride, and titanium carbide; high-purity metals are Be, Ni, Fe, Co, Mo, Cu, Pt, Au, and Ti , one or more of W.

Furthermore, the method for removing salt inclusions is one or more of water washing, acid washing, alkali washing, and distillation. Preferably, the method for removing salt inclusions is distillation.

Beneficial effects of the present invention:

1. Realize the reuse of waste beryllium, which not only makes waste beryllium harmless, but also realizes its resource utilization, generates economic benefits, and makes up for the shortage of beryllium resources in our country.

2. Compared with fire remelting, electrochemical reaction recycling has a large reaction driving force and can break bonds with large bond energy such as Be-O in waste beryllium, solving the problem of fire remelting. At the same time, electrochemical recycling The recycling control accuracy is high.

3. Use fluoride or fluorochloride molten salt to control the proportion of salt in the molten salt system and change the complex structure of beryllium ions (different bond energies will lead to different structures of complexes and the number of complex ions), It expands the potential difference between impurity ions with similar potential in the molten salt system and facilitates the separation of impurities.

4. Electrochemical recycling of waste beryllium can directly obtain metal-grade beryllium, avoiding the traditional waste beryllium-dissolution-ionization-precipitation-beryllium hydroxide/beryllium fluoride-metal beryllium process, which greatly shortens the process flow.

5. For the main dense oxide layer (Be-O) on the surface of waste beryllium, there is no need for cumbersome pretreatment such as "chipping, degreasing, pickling, and drying". Instead, it starts from the basic principles of electrochemistry and combines the components of waste beryllium and special Structure (beryllium oxide exists on the surface or grain boundaries of waste beryllium. Beryllium oxide is in the hexagonal wurtzite crystal form. The atoms are densely packed and have good stability. The distance between Be and O is very small, about 1.645x10-10m. The bond energy (large), the single bond of halogen atoms, especially the high oxidizing property of fluorine atoms, can effectively break the Be-O bond. This treatment not only improves the recycling efficiency, but also does not limit the physical form of waste beryllium, such as beryllium chips, beryllium powder and other particles, which can also be pressed into a certain shape. Moreover, pretreatments such as "chipping, degreasing, pickling, and drying", especially pickling, can destroy the oxide film, but it is still easy to form an oxide film again during drying.

6. This application directly uses waste beryllium as the anode without the aid of a titanium basket, which can avoid the introduction of unnecessary impurities (such as titanium) when the anode is dissolved.

7. This application uses a fluoride or fluorochloride molten salt system, which greatly increases the dissociation of Be-O in the electrolyte system, facilitates the cathode deposition of beryllium and the anode discharge of oxygen, and avoids the difficulty of oxygen diffusion in the chloride single molten salt system. The problem.

8. This application adds beryllium ions to the molten salt system and controls the beryllium salt concentration to keep the beryllium ion concentration relatively stable during the electrochemical process, which facilitates stable electrolysis. If there are no beryllium ions initially, it will be difficult to deposit beryllium on the cathode.

Detailed ways

The specific embodiments of the present invention will be further described in detail below with reference to examples.

Example 1

Construct a BeF ₂ -LiF molten salt system with 10at.% beryllium fluoride and 90at.% lithium fluoride, mix evenly and put it into a nickel crucible, heat to 880°C, and use waste beryllium flakes (purity is 96.0%, BeO 2.5%) as the anode, beryllium plate as the cathode, pre-reaction at a constant voltage of 2.2V in an argon atmosphere, stop after 0.5h, replace with a new cathode, continue the constant current electrochemical reaction at 880°C, and control the cathode The current density is 0.15A/cm ² , the cathode product is obtained at the cathode, and the trapped salt is removed by vacuum distillation to obtain metallic beryllium with a purity of 99.6% and a recovery rate of 81.3%.

Example 2

Construct a BeF ₂ -LiF molten salt system with 55at.% beryllium fluoride and 45at.% lithium fluoride, mix evenly and put it into a nickel crucible, heat to 400°C, and use waste beryllium flakes (purity is 95.0%, BeO 3.5%) as the anode, titanium carbide plate as the cathode, pre-reaction at a constant voltage of 2.7V in an argon atmosphere, stop after 0.5h, replace with a new cathode, continue the constant current electrochemical reaction at 400°C, control The cathode current density is 0.5A/cm ² , the cathode product is obtained at the cathode, and the trapped salt is removed by vacuum distillation to obtain metallic beryllium with a purity of 99.6% and a recovery rate of 80.2%.

Example 3

Construct a BeF ₂ -NaF-KF molten salt system with 40at.% beryllium fluoride, 30at.% sodium fluoride and 30at.% potassium fluoride. Mix evenly and put it into a platinum crucible. Heat to 800°C to The retired beryllium mirror (purity is 98.5%, BeO is 0.7%) is used as the anode, and the titanium plate is used as the cathode. Under an argon atmosphere, the pre-reaction is carried out at a constant voltage of 2.0V. It stops after 1 hour, replaces the new cathode, and continues at 800°C. Under constant current electrochemical reaction, the cathode current density is controlled to 0.8A/cm ² , and the cathode product is obtained at the cathode. It is first pickled, washed with water, and then vacuum distilled to remove the salt, and the metal beryllium with a purity of 99.5% is obtained, with a recovery rate of 83.2%.

Example 4

Construct a BeF ₂ -NaF molten salt system with 50at.% beryllium fluoride and 50at.% sodium fluoride, mix evenly and put it into a molybdenum crucible, heat to 780°C, and use powder metallurgy defective beryllium parts (purity is 98.0 %, BeO is 0.98%, Fe is 790ppm) is the anode, and the tungsten rod is the cathode. Under an argon atmosphere, pre-react at a constant voltage of 2.3V. Stop after 1 hour, replace the cathode with a new one, and continue the constant current at 780°C. In the electrochemical reaction, the cathode current density is controlled to 0.8A/cm ² , and the cathode product is obtained at the cathode. It is first washed with alkali, then washed with water, and then vacuum distilled to remove the salt, and obtain metallic beryllium with a purity of 99.9%, in which Fe ≤ 78ppm, and the recovery rate is 90%. .

Example 5

Construct a BeF ₂ -NaF-CaCl ₂ molten salt system with 60at.% beryllium fluoride, 30at.% sodium fluoride and 10at.% calcium chloride. Mix evenly and put it into a molybdenum crucible and heat it to 700°C. Use the ingot cut off from the ingot (purity 94.3%, Fe 3500ppm) as the anode, and the molybdenum plate as the cathode. Under a helium atmosphere, pre-react at a constant voltage of 2.5V. Stop after 2 hours. Replace with a new cathode and continue. Constant current electrochemical reaction at 700°C, controlling the cathode current density to 0.7A/cm ² , obtaining the cathode product at the cathode, which is first pickled and then washed with water to remove the salt, and obtain metallic beryllium with a purity of 99.8%, in which Fe ≤ 125ppm, recovery rate is 85%.

Example 6

Construct a BeF ₂ -NaF-KCl molten salt system with 50at.% beryllium fluoride, 30at.% sodium fluoride and 20at.% potassium chloride. Mix evenly and put it into a molybdenum crucible. Heat to 850°C to The ingot head cut off from the ingot (purity 92.5%, Fe 0.32%, BeO 1.33%) is used as the anode, and the molybdenum plate is used as the cathode. Under an argon atmosphere, pre-reaction is carried out at a constant voltage of 2.6V. Stop after 2 hours and replace with a new one. cathode, continue the constant current electrochemical reaction at 850°C, control the cathode current density to 1.0A/cm ² , obtain the cathode product at the cathode, remove the salt by distillation under reduced pressure, and obtain metallic beryllium with a purity of 99.3%, in which Fe≤110ppm , the recovery rate is 82%.

Example 7

Construct a BeF ₂ -BeCl ₂ molten salt system with 20 at.% beryllium fluoride and 80 at.% beryllium chloride, mix evenly and put it into a platinum crucible, heat to 450°C, and use beryllium ingot outer skin (purity 93.7%, Si 1230ppm) as the anode, titanium boride plate as the cathode, pre-reaction at a constant voltage of 3.0V in an argon atmosphere, stop after 2 hours, replace the new cathode, continue the constant current electrochemical reaction at 450°C, and control the cathode The current density is 0.1A/cm ² , and the cathode product is obtained at the cathode. It is first pickled and then washed with water to remove the salt, and the metal beryllium with a purity of 99.4% is obtained, in which Si ≤ 25ppm, and the recovery rate is 87%.

Example 8

Construct a BeF ₂ -BaF ₂ molten salt system with 20 at.% beryllium fluoride and 80 at.% barium fluoride. Mix evenly and put it into a tungsten crucible. Heat it to 950°C and cast the ingot head (purity 96.7). %, Fe is 1300ppm, BeO is 0.95%) is the anode, and the tungsten plate is the cathode. Under a neon atmosphere, pre-reaction is carried out at a constant voltage of 2.8V. Stop after 0.5h. Replace the cathode with a new one and continue to operate at a constant temperature of 950°C. Through flow electrochemical reaction, the cathode current density is controlled to 1.3A/cm ² , and the cathode product is obtained at the cathode. It is acid-washed and then washed with water. The trapped salt is removed by distillation under reduced pressure to obtain metallic beryllium with a purity of 99.7%, in which Fe ≤ 45ppm. Recovery rate is 83%.

Claims (10)

1. A method for electrochemical recovery of waste beryllium, characterized by comprising the following steps: (1) Construct a beryllium-containing fluoride or beryllium-containing fluorochloride molten salt system; (2) Using waste beryllium as an anode, perform electrochemical selective dissolution and deposition under a protective gas atmosphere to obtain a cathode product; (3) Remove the salts contained in the cathode product to obtain high-purity metal beryllium. 2. The method for electrochemical recovery of waste beryllium according to claim 1, characterized in that the beryllium-containing fluoride molten salt system is BeF ₂ -MF _n and the beryllium-containing fluorochloride molten salt system is BeF ₂ -MF _n -MCl _n , where MF _n is one or more of alkali metal fluorides or alkaline earth metal fluorides other than BeF ₂ , and MCl _n is one or more of alkali metal chlorides or alkaline earth metal chlorides. . 3. The method for electrochemical recovery of waste beryllium according to claim 2, characterized in that the BeF ₂ accounts for 10-80 at.% of the BeF ₂ -MF _n or BeF ₂ -MF _n -MCl _n molten salt system. 4. The method for electrochemical recovery of waste beryllium according to claim 2, characterized in that, the MF _n is LiF, NaF, KF, MgF ₂ , CaF ₂ , BaF ₂ , and the MCl _n is LiCl, NaCl, KCl, BeCl ₂ , MgCl ₂ , CaCl ₂ , BaCl ₂ . 5. The method for electrochemical recycling of waste beryllium according to claim 1, characterized in that the waste beryllium is leftover materials produced in beryllium ingot casting and profile processing, defective products in beryllium material production, and beryllium parts that have expired. one or more of them. 6. The method for electrochemical recovery of waste beryllium according to claim 1, characterized in that the protective gas is one of helium, argon and neon. 7. The method for electrochemical recycling of waste beryllium according to claim 1, characterized in that the temperature of the electrochemical reaction is 400-1000°C; constant current electric drive, the cathode current density of the electrochemical reaction is 0.01-3.0A/ cm ² . 8. The method for electrochemical recovery of waste beryllium according to claim 1, characterized in that, a pre-reaction is carried out before electrochemistry, the temperature is 400-1000°C, the voltage is 2.0-3.0V, the time is 0.1-2h, and the pre-reaction is Then replace the cathode. 9. The method for electrochemical recycling of waste beryllium according to claim 1, characterized in that the cathode material used in the electrochemical reaction is one of high-purity metal, high-entropy alloy, titanium boride, and titanium carbide; high-purity The metal is one or more of Be, Ni, Fe, Co, Mo, Cu, Pt, Au, Ti, and W. 10. The method for electrochemical recovery of waste beryllium according to any one of claims 1 to 9, characterized in that the method of removing salt inclusions is one or more of water washing, acid washing, alkali washing, and distillation. .