METHOD FOR REFINING BERYLLIUM BY MOLTEN SALT ELECTROLYSIS

Description

TECHNICAL FIELD

The present disclosure belongs to the field of beryllium metallurgy, and specifically relates to a method for refining beryllium by molten salt electrolysis.

BACKGROUND

Beryllium is a metal that is widely used. Among all metals, beryllium possesses the strongest penetrating ability for X-rays, earning it the nickname “metallic glass”, it is an irreplaceable material for manufacturing X-ray tube windows. Beryllium also exhibits strong neutron moderation properties, allowing fission reactions to go on continuously, making it an excellent neutron moderator in atomic reactors. When beryllium is alloyed with copper to form beryllium-copper alloy, it can be used as conductive-elastic components and elastic-sensitive components.

Currently, beryllium is primarily produced by reducing beryllium fluoride using magnesium and the obtained beryllium metal beads contain 96-97% of beryllium, further refining is required to obtain high-purity beryllium metal. Beryllium is mainly refined through vacuum volatilization in industry, however, a small amount of oxygen present in the industrial volatilization furnace reacts with exposed beryllium metal to form beryllium oxide that encases the beryllium metal surface, making it difficult to volatilize impurities like magnesium. Patent CN 109182786A discloses a method for preparing high-purity beryllium metal by volatilizing impurities in the absence of oxygen. The principle is similar to the industrial vacuum volatilization method, but the difference lies in the fact that this method purifies crude beryllium in an oxygen-free environment, however, achieving an oxygen-free environment in practice is challenging, making this method susceptible to the aforementioned drawbacks. Patent CN 109097602 A discloses a method for refining beryllium by thermal dissociation of beryllium iodide, this method first involves the low-temperature reaction of crude beryllium powder with iodine to form beryllium iodide, which is then thermally decomposed at high temperature to produce high-purity beryllium powder, this method uses a thermal dissociation reactor to purify crude beryllium powder, offering a straightforward operation, however, the reaction rate between iodine and beryllium is slow, making it difficult to obtain beryllium iodide, additionally, this method requires a vacuum, which is very demanding. U.S. Pat. Nos. 3,278,402 A and 3,296,107 A disclose methods for refining beryllium, the methods first remove impurities that are less reactive than beryllium in chloride molten salt by pre-electrolysis, and then produce beryllium metal by electrolysis, the methods can obtain high-purity beryllium, however, the beryllium will deposit during the pre-electrolysis process, leading to partial loss of beryllium, moreover, chlorine gas is produced during the electrolysis process.

SUMMARY

The purpose of the present disclosure is to provide a method based on the difference in metal redox potentials, using a liquid alloy to connect the anode chamber and the cathode chamber, and then efficiently refining beryllium by electrolysis, the method does not require a vacuum and does not need to be operated in an oxygen-free environment, the reaction conditions are easy to achieve, and there is no loss of beryllium.

To achieve the above purpose of the present disclosure, the following technical solutions are used in the present disclosure:

A method for refining beryllium by molten salt electrolysis, comprising the following steps:

- (1) Constructing an electrochemical system: the electrolytic cell is divided into an anode chamber and a cathode chamber, wherein the anode chamber contains an anode molten salt electrolyte, a crude beryllium anode is inserted in the anode molten salt electrolyte, the cathode chamber contains a cathode molten salt electrolyte, a cathode is inserted in the cathode molten salt electrolyte, a liquid alloy is at the bottom of the inside of the electrolytic cell; the anode molten salt electrolyte and the cathode molten salt electrolyte are not in contact with each other but are connected via the liquid alloy at the bottom of the inside of the electrolytic cell;
- (2) Applying a current for electrolysis, the beryllium metal in the anode is oxidized to beryllium ions, the beryllium ions from the anode are moved into the anode molten salt electrolyte, the beryllium ions in the anode molten salt electrolyte are reduced to beryllium metal at the interface between the anode molten salt electrolyte and the liquid alloy, the beryllium metal at the interface between the anode molten salt electrolyte and the liquid alloy is dissolved into the liquid alloy, meanwhile the beryllium metal in the liquid alloy is oxidized to beryllium ions at the interface between the liquid alloy and the cathode molten salt electrolyte, the beryllium ions at the interface between the liquid alloy and the cathode molten salt electrolyte are moved into the cathode molten salt electrolyte, the beryllium ions in the cathode molten salt electrolyte are reduced to beryllium metal on the cathode surface.

Preferably, the cathode is a nickel, tungsten or molybdenum cathode.

Preferably, the liquid alloy is an alloy comprised of beryllium and one or several of copper, silver, gold, manganese. Further preferably, the liquid alloy is an alloy comprised of beryllium and copper in an atomic ratio of 28:72.

Preferably, the anode molten salt electrolyte and the cathode molten salt electrolyte are the same or not the same, the anode molten salt electrolyte and the cathode molten salt electrolyte both are halide molten salts containing beryllium ions, preferably the anode molten salt electrolyte and the cathode molten salt electrolyte are both mixtures of beryllium fluoride and one or several of lithium fluoride, sodium fluoride, potassium fluoride, magnesium fluoride, and calcium fluoride.

Preferably, under the condition of applying a current, the density of both the anode molten salt electrolyte and the cathode molten salt electrolyte is lower than the density of the liquid alloy.

Preferably, the purity of the crude beryllium in the crude beryllium anode is not lower than 90%.

Preferably, the anode current density is between 0.1 A/cm2 and 1.5 A/cm2, the electrolysis temperature is between 600° C. and 1100° C. If the temperature is too low, the molten salt and the alloy will be difficult to melt, if the temperature is too high, the molten salt will volatilize in large quantities.

The beneficial effects of the present disclosure are:

- (1) The method for refining beryllium by molten salt electrolysis described in the present disclosure connects two electrolytic chambers by a liquid alloy, when the ions in the anode molten salt electrolyte are reduced into corresponding metals and enter the liquid alloy, the metals more active than beryllium enter the alloy later than beryllium, and although the metals more inert than beryllium enter the liquid alloy earlier than beryllium, when the metals in the liquid alloy are oxidized into corresponding ions and enter the cathode molten salt electrolyte, the metals more inert than beryllium are oxidized later than beryllium, therefore, the present disclosure can effectively remove impurities from crude beryllium.
- (2) In the method for refining beryllium by molten salt electrolysis described in the present disclosure, the beryllium-containing halide molten salt can isolate the air and prevent the generated beryllium metal from contacting the air, the reaction does not need to be carried out in an oxygen-free environment, moreover, the method of the present disclosure is based on electrochemical differences of different ions to remove impurities and the reaction does not require a vacuum.
- (3) The method for refining beryllium by molten salt electrolysis described in the present disclosure does not require pre-electrolysis process and there is no loss of beryllium during the reaction process.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an electrolysis device diagram of the method for refining beryllium by molten salt electrolysis described in the present disclosure;

Where, 1—anode; 2—anode molten salt electrolyte; 3—liquid alloy; 4—cathode; 5—cathode molten salt electrolyte; 6—anode chamber; 7—cathode chamber.

DETAILED DESCRIPTION OF THE EMBODIMENTS

To make the purpose, technical solutions and advantages of the present disclosure clearer, the technical solutions of the present disclosure will be described in detail below. Obviously, the described embodiments are only a part of the embodiments of the present disclosure, but are not all of the embodiments. Based on the embodiments in the present disclosure, all other implementations obtained by those of ordinary skill in the art without any creative work fall within the scope of protection of the present disclosure. Unless otherwise specified, the proportions indicated in the embodiments are mass percentages.

Embodiment 1