Method for cyclically preparing elemental boron and coproducing sodium cryolite using sodium fluoborate as intermediate material

A method for cyclically preparing elemental boron and coproducing sodium cryolite using sodium fluoborate as an intermediate material, including the following steps:

• A) adding hydrofluoric acid to boric acid or boron oxide to enable a reaction at a temperature of between 100-200° C. to form fluoboric acid;
• B) adding a sodium carbonate aqueous solution to the fluoboric acid to enable a reaction to form a sodium fluoborate solution, concentrating, crystallizing and rinsing the sodium fluoborate solution to obtain the intermediate material sodium fluoborate, and then drying the intermediate material sodium fluoborate;
• C) putting the dried sodium fluoborate into a reactor, injecting an inert gas to the reactor after vacuumizing, heating the reactor to a temperature of between 700-1000° C., adding aluminum in the reactor and stirring quickly to enable a reaction for 4 to 6 hours to form the elemental boron and sodium cryolite, or,
• putting aluminum into a reactor, injecting an inert gas to the reactor after vacuumizing, heating the reactor to the temperature of between 700-1000° C., adding the dried sodium fluoborate in the reactor and stirring quickly to enable a reaction for 4 to 6 hours to form the elemental boron and sodium cryolite;
• D) extracting a molten liquid sodium cryolite, after it is cooled, crushing and sending it to a rotary reaction kettle quantificationally together with concentrated sulphuric acid to enable a reaction at a temperature of between 400-500° C. to form hydrogen fluoride gas and aluminum aluminium sodium sulphate;
• collecting the hydrogen fluoride gas and dissolving it into water to obtain a hydrofluoric acid aqueous solution;
• reacting the aluminum sodium sulphate with an aqueous solution of sodium hydroxide after crushing the aluminum sodium sulphate, and obtaining an aqueous solution of sodium sulphate after separating out a solid aluminum hydroxide;
• and
• E) recycling the obtained hydrofluoric acid aqueous solution to leach the boric acid or boron oxide, so as to prepare additional sodium fluoborate.