Abstract
Current industrial processes of tantalum (Ta) and niobium (Nb) extraction from primary resources rely in majority on hydrofluoric (HF) acid leaching, which is raising material handling and safety issues. In this work, a novel HF-free treatment route for a coltan ore, based on alkaline roasting, water-leaching, precipitation, and oxalic leaching is presented. A raw ore from Lulingu deposit (the Democratic Republic of the Congo) was subjected to alkaline roasting followed by water leaching to bring Ta and Nb into solution. The most influential operating parameters of the roasting were outlined using Taguchi orthogonal array L16 (44) method. The optimal roasting conditions determined as temperature (450 °C), roasting time (2 h), molar ratio KOH/(Ta,Nb)2O5 of 13.2 (e.g., mass ratio KOH to ore of about 2/1) and granulometric fraction (− 105 + 75 µm), enabled about 87% of Ta and 92% of Nb to be subsequently water leached. The resulting alkaline pregnant leach solution (PLS) was subjected to precipitation, followed by oxalic acid leaching of the formed precipitates. This step brought about 86% of Ta and 92% of Nb in solution confirming the efficiency of the method. Globally, an extraction efficiency of ca. 75% for Ta and 84% for Nb could be expected from the entire process. In addition, the obtained Ta–Nb leachate was deemed suitable to downstream solvent extraction in view yielding high-purity Ta2O5 and Nb2O5 compounds.
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Acknowledgements
This work was supported by the ARES Academy (Belgium) within the PRD 2019 ARES-CCD project. Prof. Fr. Hatert, Dr. H. Bouzahzah, and Dr. J.L. Colaux are gratefully acknowledged for their support with the mineralogical inspection. A. S. and F. Z. would like to thank the CEGEMI team led by Prof. Marie Rose Bashwira for their assistance during the coltan sampling campaign.
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AS: experiments execution, data compilation, and writing the initial draft. FZ: ore sampling, and materials preparation. FAM: background, data supply, and conceptualization. MM: background, data supply conceptualization, and additional samples preparation for elemental analysis. MA: experimental set-up, results discussion. SG: experiments planning, formulation of research aims, and paper concept as well as final paper polishing.
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Shikika, A., Zabene, F., Muvundja, F.A. et al. Efficient Extraction of Ta and Nb from a Coltan Ore Through Alkaline Roasting, Water Leaching, Precipitation, and Oxalic Acid Leaching. J. Sustain. Metall. 8, 1932–1947 (2022). https://doi.org/10.1007/s40831-022-00621-w
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DOI: https://doi.org/10.1007/s40831-022-00621-w