METHOD FOR HYDROLYTIC PURIFICATION OF BISMUTH Russian patent published in 2025 - IPC C01G29/00 C22B30/06 C22B3/44 

FIELD: chemistry.

SUBSTANCE: invention relates to purification of bismuth from impurity metals to obtain bismuth metal of high purity. Metal bismuth is dissolved in nitric acid in the presence of ammonium nitrate. For hydrolytic purification, the obtained bismuth nitrate solution is added to hot water. Mother solution is obtained, which is separated from the precipitate. Precipitate is washed with a solution of nitric acid and double-distilled water. Precipitate of basic bismuth nitrate is dried, calcined to an oxide and the obtained oxide is reduced in molten sodium hydroxide containing sulphur. Bismuth is precipitated from the mother solution by adding ammonium carbonate solution thereto. Obtained precipitate is washed with a solution of nitric acid and double distilled water, the precipitate of basic bismuth nitrate is dried, annealed and the obtained oxide is reduced in molten sodium hydroxide containing sulphur. Ammonium carbonate solution is added to the mother and washing solutions. Solution is separated from the precipitate and the precipitate is directed to a step for dissolving bismuth metal. Ammonium carbonate solution is added to the obtained solution, the solution is filtered from the precipitate and the obtained ammonium nitrate solution is sent to a step for dissolving bismuth metal.

EFFECT: method simplifies the process, eliminates release of toxic nitrogen oxides into the gas phase at the stage of dissolving bismuth metal, allows to obtain Bi 000 (not less than 99.999% bismuth) and Bi 00 (not less than 99.98% bismuth), as well as fully use bismuth and ammonium nitrate solution in production of basic bismuth nitrate.

1 cl, 1 ex