Vatolin Institute of Metallurgy of the Ural Branch of the Russian Academy of Sciences (Ekaterinburg, Russia)

Pikulin K. V., Candidate of Technical Sciences, Senior Researcher, pikulin.imet@gmail.com
Tyushnyakov S. N., Candidate of Technical Sciences, Leading Researcher
Fedorov S. A., Candidate of Technical Sciences, Senior Researcher
Gulyaeva R. I., Candidate of Chemical Sciences, Senior Researcher
Sergeeva S. V., Candidate of Technical Sciences, Senior Researcher
Udoeva L. Yu., Candidate of Technical Sciences, Leading Researcher

Under conditions of sustained growth in global demand for niobium and tantalum, the involvement of new deposits in processing and the development of efficient extraction technologies for these metals are becoming particularly relevant. Traditional hydrometallurgical schemes are well-established for rich concentrates; however, their application to low-grade raw materials and technogenic formations is associated with technological and economic challenges. A promising approach appears to be pyrometallurgical processing with recovery of valuable components into a metal concentrate (alloy) via aluminothermic reduction. This study examines the aluminothermic reduction of tantalum and niobium using natural columbite-tantalite (coltan) as an example – one of the principal ore minerals of industrial significance for tantalum-niobium raw materials. Results of a comprehensive investigation into the material composition of the sample and its influence on the efficiency of aluminothermic metal recovery are presented. It was established that niobium and tantalum in the studied coltan sample occur within the minerals columbite-tantalite and tapiolite, which differ in their crystal structures. Tin is present as cassiterite and partially as an isomorphic impurity in tantalite. Experimental results demonstrate that the interaction of coltan's mineral components with aluminum depends on their crystallochemical stability: the degree ofm etal recovery from columbite-tantalite is significantly higher than from tapiolite. The maximum extraction of Nb and Ta into the alloy without flux addition reached 93.0 % and 86.3 %, respectively; with the addition of calcium oxide for slag formation, these values decreased to 73.9 % and 85.3 % due to the formation of rare-metal calcium aluminates. In both cases, “benefication” of the reduction product (alloy) with target metals was observed, while the contents of accompanying components (Fe, Mn, Sn) remained virtually unchanged relative to the feed. Aluminothermic processing of tantalum-niobium raw materials can be considered an alternative pyrometallurgical benefication method, suitable for both standard-grade and low-grade rare-metal concentrates.

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