National Research Nuclear University MEPhI, Moscow, Russia:

A. V. Valkov, Professor at the Department of General Chemistry, Doctor of Engineering Sciences, e-mail: ale11534@yandex.ru

The rare earth metals (REMs) found in apatite, loparite and the concentrates from the Tomtor deposit may lay the basis for expanding the Russian rare earths industry. The most sellable REMs with an almost unlimited demand include neodymium, praseodymium, dysprosium and terbium. They account for ~80% of the extracted individual REMs sold. It is proposed to design a processing sequence enabling to extract the above elements at minimal cost reaching maximum purity. The rest of the REMs are considered a poorly sellable product. A sequence is proposed to separate REM concentrates recovered from loparite, apatite or the concentrate from the Tomtor deposit, which involves separation of praseodymium mixed with neodymium (didymium) and terbium mixed with dysprosium (dysterbium) with the concentration of the base material being 99.95–99.99 wt%. It was decided to use the system of 100% tributyl phosphate – Ln(NO₃)₃ – Са(NO₃)₂ — to separate didymium, and the organophosphorus acid (OPA) based system: i. e. 30% OPA – Ln(NO₃)₃ – HNO₃ -to separate dysterbium. The author examined how the centrifugal coefficient, the pure component extraction ratio and the purity of extracted elements determine the required number of stages. The process consists of four extraction cascades. Separation at the praseodymium–cerium boundary is performed without pre-separation of cerium. To separate dysterbium, they separate holmium and heavier REMs in one cascade, and gadolinium and lighter REMs – in the second cascade. The following products are obtained as a result of separation: lanthanum-cerium concentrate, didymium, dysterbium, samarium-europium-gadolinium concentrate and a concentrate of yttrium REMs from holmium to lutecium.

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