METHOD FOR PROCESSING PHOSPHOGYPSUM, CONTAINING PHOSPHOROUS COMPOUND AND LANTHANIDES Russian patent published in 2008 - IPC C01F11/46 

FIELD: chemistry.

SUBSTANCE: invention pertains to the technology of complex processing of phosphogypsum, obtained during sulphuric acid conversion of apatite concentrate to mineral fertilisers. Phosphogypsum is leached by a 22-30% solution of sulphuric acid for a period of 20-25 minutes, turning phosphorous and lanthanides into a leaching solution and a gypsum residue is obtained. The gypsum residue is separated from the leaching solution by centrifuging until residual moisture of not more than 20% is attained, after which the gypsum is treated with a basic calcium compound to pH of more than 5. Later, by crystallisation, a concentrate of lanthanides, which is separated from the mother solution, is separated from the leaching solution. The content of phosphorous impurities in the mother solution is controlled, and if the product x·y < 180, where x is the content of phosphorous impurities in the mother solution in terms of P₂O₅ (g/l), y is the residual moisture of the gypsum residue (%), the mother solution is taken to the leaching stage, and if the product x·y ≥ 180, the mother solution is cleaned first. Cleaning the mother solution from phosphorous is done by adding it to a solution of a titanium compound in quantity defined by: 2.5·(x-5) g/l, with separation of the formed hydrated titanyl phosphate.

EFFECT: increasing efficiency of processing phosphogypsum due to reduced cost and number of reagents and lower power input of the process, with simultaneous increase in the degree of extraction of lanthanides in the leaching solution up to 82.1%, and simplification of the method.

6 cl, 5 ex