Journals →  Tsvetnye Metally →  2015 →  #11 →  Back

RARE METALS, SEMICONDUCTORS
ArticleName Research of equilibrium in the system (NH4)3ScF6 – NH4HF2 – H2O
DOI 10.17580/tsm.2015.11.08
ArticleAuthor Sokolova Yu. V., Pirozhenko K. Yu.
ArticleAuthorData

National University of Science and Technology “MISiS”, Moscow, Russia:

Yu. V. Sokolova, Leading Researcher
K. Yu. Pirozhenko, Post-Graduate Student, e-mail: pirozhenkok@yandex.ru

Abstract

Rough concentrates, containing from tenths to few percents of scandium (hydrate, carbonate or fluoride settings) are obtained on the first stage of accompanying scandium extraction during the complex processing of rare metal ores (tungsten, niobium and tantalum, uranium, titanium, zirconium) and other raw materials. Further processing of these concentrates shows the reasonability of application of the reagents, making possible the scandium leaching without transfer of the basic accompanying elements (aluminium, calcium, rare-earth elements, thorium, etc) into solution. Equilibrium in the system (NH4)3ScF6 – NH4HF2 – H2O at the temperatures of 18 and 90 °С was investigated for the purpose of definition of the parameters of the process of scandium leaching from its concentrates by NH4HF2 solution. Investigations used the (NH4)3ScF6, obtained during the interaction of ScF3 with NH4F solution. Isotherms of (NH4)3ScF6 solubility were made for the interval of concentrations of 0.05–3.50 mole/l of NH4HF2 and the temperatures of 18 and 90 °С. Equilibrium in the system was reached during 2.5–3 hours. There was made a definition that dissolution of (NH4)3ScF6 in the investigated conditions is incongruent. The compositions of obtained settings of bottom phases were investigated. For the first time, a new phase of (NH4)5Sc3F14 compound was isolated from the solution; its existing areas and crystallographic characteristics were defined. In both cases, dissolubility isotherms have the expressed maximums. At the temperature of 18 °С, the maximum corresponds to the concentration of 1 mole/l of NH4HF2 and 0.137 mole/l of Sc. Setting at the maximum point is shown by (NH4)3ScF6; while settings above and below the maximum point are shown by (NH4)5Sc3F14 and (NH4)3ScF6, respectively. Dissolubility isotherm has two maximums at the temperature of 90 °С: concentration of 0.4 mole/l of NH4HF2 (0.253 mole/l of Sc, setting — (NH4)5Sc3F14; above the maximum point in the setting — NH4ScF4), and concentration of 1.5 mole/l of NH4HF2 (0.311 mole/l of Sc, setting — (NH4)3ScF6 with impurity of (NH4)5Sc3F14; with NH4HF2 concentration growth in the setting – initial compound).

keywords Scandium, leaching, scandium fluoride, ammonium hydrofluoride, ammonium hexafluoscandate, incongruent solubility, congruent solubility
References

1. Wang W., Pranolo Y., Cheng C. Y. Metallurgical processes for scandium recovery from various resources: a review. Hydrometallurgy. 2011. Vol. 108. pp. 100–108.
2. Wang W., Pranolo Y., Cheng C. Y. Recovery of scandium from synthetic red mud leach solutions by solvent extraction with D2EHPA. Separation and Purification Technology. 2013. Vol. 108. pp. 96–102.
3. Huang Guiyong. Method for obtaining scandium-rich material from acidic wastewater of titanium dioxide environment-friendly workshop. Patent CN, No. 102976527. Published: March 20, 2013.
4. Liu Z., Li H. Metallurgical process for valuable elements recovery from red mud — a review. Hydrometallurgy. 2015. Vol. 155. pp. 29–43.
5. Sokolova Yu. V., Pirozhenko K. Yu., Makhov S. V. Concentration of scandium during processing the sublimate of production of the aluminumscandium master alloy. Russian Journal of Non-Ferrous Metals. 2015. Vol. 56, Iss. 1. pp. 10–14.
6. Sokolova Yu. V., Cherepanin R. N. Leaching-out of scandium (III) in processing of a fluoride concentrate. Russian Journal of Applied Chemistry. 2006. Vol. 79, Iss. 6. pp. 890–892.

7. Ivanov-Emin B. N., Susanina T. N., Ogorodnikova L. A. Issledovanie vzaimodeystviya soley skandiya s ftoridom ammoniya (Investigation of interaction of scandium salts with ammonium fluoride). Zhurnal neorgicheskoy khimii = Russian Journal of Inorganic Chemistry. 1966. Vol. 11, No. 3. pp. 504–509.
8. Ivanov-Emin B. N., Susanina T. N., Ezhov A. I. Issledovanie ftorskandiatov ammoniya (Investigation of ammonium fluorscandiates). Zhurnal neorgicheskoy khimii = Russian Journal of Inorganic Chemistry. 1967. Vol. 12, No. 1. pp. 23–29.
9. Hajek B. Weitere Erkenntnisse über das Scandiumdiphosphat. Zeitschrift für anorganische und allgemeine Chemie. 1963. Bd. 3. ss. 194–195.
10. Champarnaud-Mesjard J., Frit B. Les systemes MF–ScF3 (M  Li, Na, K, Rb, Cs, Tl, NH4). Journal of the Less-Common Metals. 1991. Vol. 167, Iss. 2. pp. 319–327.
11. Mikhaylov M. A., Epov D. G., Sergienko V. I., Rakov E. G., Shchetinina G. P. Termogravimetricheskoe issledovanie ammoniynykh kompleksnykh ftoridov skandiya i ittriya (Thermal-gravimetric investigation of ammonium complex fluorides of scandium and yttrium). Zhurnal neorgicheskoy khimii = Russian Journal of Inorganic Chemistry. 1973. Vol. 18, Iss. 6. pp. 1508–1512.
12. Stephens N. F., Lightfoot P. Hydrothermal scandium fluoride chemistry: syntheses and crystal structures of [C2N2H10][ScF5], [NH4]2[Sc3F11] and [H3O] [C6N2H16][ScF6]·H2O. Solid State Sceinces. 2006. Vol. 8, Iss. 2. pp. 197–202.
13. Bode H., Voss E. Strukturen der Hexafluorometallate (III). Zeitschrift für anorganische und allgemeine Chemie. 1957. Bd. 290. ss. 1–16.
14. Boehmer N., Meyer G. Die Einwirkung von Ammoniumfluorid auf Scandium: Synthese und Kristallstrukturen von (NH4)3[ScF6] und [Cu(NH3)4]3[ScF6]2. Zeitschrift für anorganische und allgemeine Chemie. 2001. Bd. 627. ss. 1248–1252.
15. Shelekhov E. V., Sviridova T. A. Programmy dlya rentgenovskogo analiza polikristallov (Programs for the X-ray analysis of polycrystals). Metallovedenie i termicheskaya obrabotka metallov = Metal Science and Heat Treatment. 2000. No. 8. pp. 16–19.
16. Sviridova T. A., Sokolova Yu. V., Pirozhenko K. Yu. Crystal structure of (NH4)5Sc3F14. Crystallography Reports. 2013. Vol. 58, No. 2. pp. 220–225.

Language of full-text russian
Full content Buy
Back