METHOD OF EXTRACTING RARE-EARTH CONCENTRATE FROM APATITE Russian patent published in 2012 - IPC C01F17/00 

FIELD: chemistry.

SUBSTANCE: invention relates to complex processing of phosphate material, particularly methods of extracting rare-earth elements from apatites. The method involves decomposition of apatite with nitric acid, freezing, separating calcium nitrate tetrahydrate crystals, deposition and separation of fluorine from the nitrate-phosphate solution, neutralisation of the purified solution with ammonia gas in two steps, separating the residue of phosphate concentrate of rare-earth elements and washing with water. Neutralisation of the nitrate-phosphate solution is carried out at temperature 85-95°C to final pH of 1.8-2.2. Before neutralisation, 55-92% ammonium nitrate solution is added in amount of 2-5% of the weight of the solution per 100% ammonium nitrate. Before separation from the suspension, the residue ages in 1-4 hours at temperature 60-80 °C. After separation from the mother solution, the residue is washed with acidified water using a repulping technique.

EFFECT: high content of rare-earth elements in the concentrate with high degree of extraction thereof from apatite.

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