Moscow State University of Fine Chemical Technologies, Moscow, Russia:

G. V. Zimina, Senior Researcher1, e-mail: gzimina@mail.ru

JSC “Akron”, Veliky Novgorod, Russia:

I. I. Nikolaeva, Deputy Head of Central Chemical Laboratory

M. V. Tauk, Chief Development Officer

This article shows the review of main extraction schemes, used for separation of rare earth elements. It is noted that all types of extracting agents (neutral extracting agent, organic acids and basics) are used for separation of rare-earth elements. Neutral organophosphorus compounds (especially tributyl phosphate) are most widely used among neutral extracting agents. Rare earth elements' extraction by tributyl phosphate from dilute acidic (0.001– 0.500 mol/l) and concentrated HNO₃ solutions is considered together with influence of rare-earth elements concentration in initial solution on separation factors, and role of salting-out and diluting agents. Difference of extraction mechanisms in the area of low and high HNO₃ concentrations is noted. There is considered the use of monobasic organophosphorus acids ((RO)₂POOH– dialkyl phosphorus, (RO)RPOOH — dialkylphosphonic and R₂POOH — dialkylphosphinic, where R is alkyl or aryl radical), which are characterized by high selectivity. It is shown, that polyamineacetic acids (EDTA, NTA, DTPA) create strong complexes with rare earth elements, while stability constant of adjacent element complexes are completely differed, which determines the usage of these elements in extraction. Usage reasonability of neutral and alkylphosphate acid mixtures for rare earth elements extraction is shown. The main principles of binary extraction are considered, which defines the obtaining of biggest separation efficiency, using dialkylphosphonates of quaternary ammonium bases as binary extracting agents.

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