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Chemistry for Sustainable Development

2016 year, number 6

Technological Cascade for Purification of Zirconium Tetrafluoride from Hafnium Using Zirconium Dioxide

I. Yu. RUSAKOV1, A. S. BUYNOVSKIY1, V. L. SOFRONOV1, L. M. LEVCHENKO2
1Seversk Technological Institute, Seversk, Russia
2Nikolaev Institute of Inorganic Chemistry, Siberian Branch, Russian Academy of Sciences, Novosibirsk, Russia
Keywords: фторидная технология, сублимация, тетрафториды циркония и гафния, диоксид циркония, хемосорбция, очистка, десублимация, технологический каскад, fluoride technology, sublimation, zirconium and hafnium tetrafluorides, zirconium dioxide, chemisorption, purification, desublimation, technological cascade

Abstract

A chemisorptive purification method of zirconium tetrafluoride from hafnium by passing vapours of the initial mixture of zirconium tetrafluoride and hafnium tetrafluoride through a sorbent layer from zirconium dioxide was proposed and investigated. Herewith, the exchange interaction of hafnium tetrafluoride vapours with solid powdery zirconium dioxide and the formation of volatile zirconium tetrafluoride (ZTF) and nonvolatile hafnium dioxide occur. Thermodynamics of the process was considered and the possibility of the exchange interaction between zirconium dioxide and hafnium tetrafluoride (HTF) was demonstrated. The thickness of a layer of zirconium dioxide required for the preparation of both nuclear purity ZTF by the content of hafnium (0.01 mass % and less) and a hafnium concentrate with a concentration of almost 100 % in zirconium dioxide was experimentally defined. Based on the experimental data, the equilibrium coefficient of a chemisorption separation process of zirconium and hafnium tetrafluorides was calculated. The technological cascade consisting of three major knots was calculated using the equilibrium coefficient - purification knot of ZTF from HTF, preparation knot of a hafnium concentrate and fluorination knot. This cascade is waste-free and allows utilizing zirconium production wastes. The chemisorption purification method of ZTF from HTF and technological cascade scheme are protected by patents of the Russian Federation.