Autoclave Leaching of Rare-Earth Metals from Hydroxide Precipitate.

Results of experiments on autoclave leaching of rare earth metals (REM) from hydroxide precipitate, obtained after alkaline atmospheric leaching ores of Tomtor deposit, are presented. It is established that autoclave leaching in the presence of oxygen makes it possible to increase the efficiency and selectivity of the process and to increase REM extraction by up to 10-13%. The main parameters of autoclave nitric acid leaching are as follows: initial HNO3 concentration 350 g/dm3; temperature 120°C; oxygen partial pressure 0.3 MPa; L:S = 5.0 (wt.); time 2 hours. In the optimum regime selected, 98.0-98.5% of REM is extracted into solution. [ABSTRACT FROM AUTHOR]