Leading Scientific-Research Chemical Technology Institute, Moscow, Russia:

I. D. Akimova, Leading Researcher, e-mail: akimovaid@vniiht.ru
G. M. Chumakova, Senior Researcher
T. V. Molchanova, Head of Laboratory, e-mail: molchanovatv@vniiht.ru

LLC “Titanovye investitsii”, Moscow, Russia:
V. V. Golovko, Deputy Head of Chemical Department for New Projects, e-mail: golovko@tioinvest.ru

This paper investigated the process of scandium extraction from hydrolyzed sulphuric acid which is a by-product of titanium dioxide pigment production while ilmenite processing at LLC “Titanovye investitsii”. Scandium concentration in the hydrolyzed sulphuric acid solution varied between 15 and 18 mg/dm³, titanium concentration was about 2–3 g/dm³, REE concentration was about 40 mg/dm³, and H₂SO₄ concentration was about 300 g/dm³. Mixtures of D2EHPA with TBP in kerosene and mono-(2-ethylhexylester)2-ethylhexyl phosphonic acid (Р507) with TBP were studied as extractants in different ratios. The best scandium extraction was obtained for mixture of 0.15 mol/dm³ + 0.075 mol/dm³ TBP in kerosene, while REE extraction under similar conditions was the worst. On the contrary, the solution of 0.15 mol/dm³ Р507 + 0.075 mol/dm³ TBP extracted REE with К_рΣRRE = 9 and almost no scandium. The experiments showed an increase of emulsification in the course of extraction without pretreatment of the original solution. Such effect was due to the presence of humic acids in the solution which contribute to the formation of a stable emulsion when organic and aqueous phases are blended. A new method to prevent the emulsion formation was offered consisting in adding waterrepellent liquid (ГКЖ-11П) in the amount of 0.2 kg/m³ and followed by decantation or filtration of the solution. The extraction was carried out with a ratio О:L = 1:8÷10 during 3 minutes. Scandium concentration in the extract was 0.08–0.12 g/dm³ and 0,001–0,003 g/dm³ in the raffinate. Stripping was combined with sedimentation of scandium concentrate. Study of the process conditions proved advantages of the solution 3% NaОН + 6% Na₂CO₃. Formation of the concentrate sediment occurred at t = 60–80 ^oC within 30 minutes. After filtering and sediment washing the obtained scandium concentrate samples contained 2.5–3.5% Sc₂O₃ at concentration 23–38% TiO .

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