METHOD OF RECOVERING RARE-EARTH ELEMENTS FROM PHOSPHOGYPSUM Russian patent published in 2007 - IPC C22B59/00 C22B3/08 

FIELD: rare-earth element technology.

SUBSTANCE: invention relates to technology of recovering rare-earth elements from phosphogypsum obtained from processing of apatite concentrate into mineral fertilizers. Phosphogypsum is treated with 22-30% sulfuric acid solution at liquids-to-solids ratio 1.8-2.2 to recover rare-earth elements and sodium into solution. Insoluble precipitate is separated and degree of oversaturation of solution regarding rare-earth elements is increased by means of providing sodium concentration 0.4-1.2 g/L, after which crystallization of rare-earth element concentrate is allowed to proceed and concentrate is then separated from mother liquor. Treatment duration is 20-30 min to prevent spontaneous crystallization of rare-earth element concentrate in solution before insoluble precipitate is separated. Content of sodium in solution is controlled by adding a sodium salt thereto, preferably sodium sulfate or sodium carbonate. Degree of recovery of rare-earth elements from phosphogypsum into concentrate achieves 71.4%.

EFFECT: increased degree of rare-earth element recovery and simplified procedure due to eliminated operation of dilution of recycle sulfuric acid solutions and shortened sulfuric acid treatment duration by a factor of 2-3.

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