Сверхкритические флюиды. Теория и практика
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2015, N2, pp. 40-50

M.D. Samsonov, T.I. Trofimov, Yu.M. Kulyako, D.A. Malikov, B.F. Myasoedov

Supercritical Fluid Extraction of Rare Earth Elements, Thorium and Uranium from Monazite Concentrate and Phosphogypsum Using Carbon Dioxide Containing Tributyl phosphate and Di-(2-Ethylhexyl)phosphoric Acid

Supercritical fluid extraction (SCFE) using carbon dioxide containing tributyl phosphate (TBP) and di-(2-ethylhexyl)phosphoric acid (D2EHPA) or their adducts with HNO3 is proposed as a method to extract rare earth elements (REE), Th and U from monazite concentrate (MC) and phosphogypsum (PG). On the first stage, the product of baking the MC with Na2CO3 (MCS) is obtained in the presence of coal under microwave irradiation, in which phosphates of REE, Th and U present in the MC are converted into their oxides. Up to 50 % of REE can be recovered from the powdered MCS by the adducts of TBP and D2EHPA with HNO3 in SCFE conditions, whereas Th and U remain in the solid phase. After a complete dissolution of the MCS residue in the mixture of 4 M HCl and 0.05 M HF, Th and U are quantitatively extracted using supercritical carbon dioxide containing D2EHPA and thus separated from the REE that remain in an acidic solution. The conditions of quantitative isolation of REE, Th and U from PG are determined and the schemes for complex processing of MC and PG targeted to the recovery of REE separated from Th and U are suggested.

Key words: supercritical fluid extraction, microwave radiation, rare earth elements, thorium, uranium, carbon dioxide, monazite concentrate, phosphogypsum, tributyl phosphate, di-(2-ethylhexyl)phosphoric acid

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