Abstract

CHIWESHE, T.T.; MOKHAHLANE, L.S.  and  WELMAN-PURCHASE, M.. Kinetic study of reaction formation of phosphate products from thermal dissolution of wolframite using fusion technique. J. S. Afr. Inst. Min. Metall. [online]. 2024, vol.124, n.6, pp.339-347. ISSN 2411-9717.  https://doi.org/10.17159/2411-9717/3215/2024.

This study examined an alternative technique of extracting tungsten from wolframite ore using a fusion method with ammonium phosphate salt. Current techniques use alkali salts to decompose tungsten ores and use various purification methods to produce ammonium paratungstate, which is a key intermediate precursor in the extraction of tungsten. In this study, a two-step extraction process, which involves thermal decomposition of the ore using fusion and a separation stage, is examined. The novelty of this technique is the ability to completely decompose wolframite ore and form an unstable tungsten oxide phosphate (WO₂(PO₃)₂) compound. The instability of WO₂(PO₃)₂ in deionized water enables selective isolation of tungsten as insoluble precipitates of WO₃ and WO₂. The decomposition reaction of WO₂(PO₃)₂ is influenced by the presence of oxygen and determined to be first order under ambient conditions. Scanning electron micrographs and X-ray diffraction analysis showed above 80% of the tungsten precipitated compared with the amount that remained in the filtrate solution.

Keywords : tungsten; tungsten oxide phosphate; wolframite ore; fusion extraction; ammonium phosphate flux.

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