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Technical
Note Removal of Radioactive
Elements from Niobium and Tantalum Ores
The production of niobium and tantalum elements from their ores requires
separating from the accompanying elements and purification. The ore material
obtained from the Eastern-Desert of Egypt consists of euxenite, betafite,
thorite and zircon. It was decomposed by sulfuric acid digestion and
portions of its constituents were transferred to the leach liquor as given:
66.8% Nb2O5, 38.7% Ta2O5, 76% rare earths,
28.9% TiO2, 86.5% ThO2 and 91.1% U3O8;
while ZrO2 remained in the unattacked residue. Liquid-liquid extraction was
performed to remove the radioactive elements from the leach liquor, leaving
niobium, tantalum and rare earths unextracted. The system sulfuric acid -diethylhexyl
phosphoric acid / tributyl phosphate in kerosene was efficient to extract
both thorium and uranium. The extraction was performed by contacting the
sulfate leach liquor of pH =1.0 and 6.6M SO42- with 0.2M D2EHPA/TBP in the
ratio A:O=3:1 for 15 minutes. The separation of thorium from uranium was
performed by two different stripping steps to obtain recovery of 99.6% ThO2
and 91.2% U3O8. On the other hand zircon of 96% purity was separated from
the unattacked residue by successive chemical treatments. |
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