METHOD OF RECOVERING RARE-EARTH MINERALS FROM PHOSPHOGYPSUM

摘要

FIELD: valuable metals' recovery methods in mining industry. SUBSTANCE: invention relates to technology of recovering rare-earth minerals from phosphogypsum obtained from sulfuric acid treatment of apatite concentrate to produce mineral fertilizers. Essence of invention resides in consecutively conducting etching of several portions of phosphogypsum using the same 20-25% sulfuric acid solution at ratio of liquid to solid components equal to 2-3 and resulting in transfer of rare-earth minerals into solution. Thus obtained etching solution is treated at 20-80 C with sulfuric acid by increasing its concentration in solution to at least 30% thereby inducing crystallization of rare-earth mineral concentrate. Crystallization is preferably effected for 0.5 to 3.0 h in presence of rare-earth element sulfate seeds at liquid-to-solids ratio no higher than 100. Resulting concentrate is separated by filtration and treated with calcium nitrate or chloride to give concentrated solution of rare-earth element nitrates or chlorides. Solution obtained after separation of rare-earth mineral concentrate is suitable for etching of phosphogypsum. Concentrates contain 30.1-44.7% of rare-earth minerals. EFFECT: increased method efficiency due to reduced power consumption, elevated contents of rare-earth minerals in concentrates, and enabled preparation of rare-earth mineral nitrate and chloride solution suitable for subsequent processing and use. 4 cl, 1 tbl, 4 ex