METHOD OF INCREASING CONCENTRATION OF RARE-EARTH ELEMENTS IN SOLUTION BY CASCADE TREATMENT OF PHOSPHOGYPSUM Russian patent published in 2025 - IPC C22B59/00 C01F17/10 C22B3/06 

FIELD: chemistry.

SUBSTANCE: invention relates to chemical industry and production of concentrates of rare-earth elements from phosphogypsum which is a waste from production of phosphoric acid. Proposed method comprises 2 steps. First step includes cascade leaching, wherein phosphogypsum sieved through a sieve with cell size of 0.16 mm is poured into 1.75 molar solution of nitric acid with ratio of solid to liquid substance of 1:2, heated to the boiling point of nitric acid solution and held 10 min. Phosphogypsum is heated in nitric acid solution on a water bath. Hot solution of phosphogypsum in nitric acid is then separated into a solid and a liquid fraction by filtering. Remaining liquid fraction of 1.75 molar solution of nitric acid rich in rare-earth elements is filled with a new batch of sieved phosphogypsum with ratio of solid to liquid substance equal to 1:2. 4 cascade leaching reactions are performed. Liquid fraction is cooled and filtered for removal of sediment in the form of calcium. Obtained liquid fraction at second step is evaporated by 90% for 50 minutes at temperature 110 °C to obtain aqueous solution of nitric acid and a solution of rare-earth elements with concentration of 43 g/l and pH equal to 5.

EFFECT: higher concentration of rare-earth elements in solution and return of nitric acid.

1 cl, 1 dwg, 3 ex