Leaching of rare earth metals (REMs) from Korean monazite concentrate

Systematic scientific studies for dephosphorization and acid leaching of Korean monazite are reported here. 50% NaOH (w/v) solubilizes 99.99% phosphate, at 170 °C, 100 g/L pulp density in 4 h. Kinetics of phosphate leaching fitted well with model “chemical reaction control,” i.e. 1 − (1 − X)1/2 = kct, Ea = 58.04 kJ/mol. Further, rare earth hydroxides (REHs) was leached using 6 N HCl at 90 °C, 60 g/L pulp density for 2 h to recover ∼95% REMs. Leach liquor generated can be further processed using solvent extraction/ion exchange techniques. From the pure solutions, metal/salts could be obtained using evaporation, precipitation, etc.