METHOD OF EXTRACTING RARE-EARTH METALS AND PRODUCING GYPSUM PLASTER FROM PHOSPHOGYPSUM HEMIHYDRATE Russian patent published in 2014 - IPC C22B59/00 C22B3/06 

FIELD: chemistry.

SUBSTANCE: method includes leaching rare-earth metals into a solution with recrystallisation of phosphogypsum from a calcium sulphate hemihydrate or anhydrite into a dihydrate. Leaching is carried out in a calcium salt solution in concentration of 0.075-3.75 M with respect to Ca²⁺ and a strong acid with pKa<0 in concentration of 0.2-8 M with respect to H+. The degree of extraction of rare-earth metals into the solution is less than 98% and the residual content of phosphorus, fluorine and alkali metal impurities in the calcium sulphate dihydrate is not more than 0.3 wt %, 0.1 wt % and 0.05 wt %, respectively.

EFFECT: more effective extraction of rare-earth metals with simultaneous purification of calcium sulphate from phosphorus and fluorine impurities.

4 cl, 3 tbl, 9 ex