| 摘要 |
<p>Tin smelting slags containing tantalum and niobium oxides are digested with aqueous sulphuric acid initially containing from 0.5 to 10% by weight of H2SO4 at at least 50 DEG C. and the tantalum oxide- and niobium oxide-containing residue is recovered. The slag may first be ground to about 95% through a 325 mesh (Tyler Standard screen size) and the stoichiometric proportion of acid to slag (based on its alumina, lime, ferric oxide, silica, titania and zirconia content) may be from 0.5 to 3.0. Temperatures of up to the boiling point of the liquors may be used and, under pressure, even higher temperatures may be employed. The residue may then be directly digested with hydrofluoric acid in the known manner.</p> |
