Purification of tantalum compounds by combining with a fluoride-containing compound, other than hydrofluoric acid, and sulfuric acid to form a solution and then separating off the tantalum content

摘要

Purification of tantalum (Ta) compounds involves: (a) combining the impurity-containing Ta compound with a fluoride-containing compound and sulfuric acid (H2SO4) to form a solution, the Ta compound being Ta oxide or hydroxide and/or a hydrated ammonium Ta oxide and the fluoride compound being ammonium bifluoride (NH4HF2), sodium fluoride (NaF), potassium fluoride (KF) and/or calcium fluoride (CaF2); and (b) separating the Ta content from the impurities. Independent claims are also included for purifying Ta compounds by: (i) combining impure hydrated ammonium Ta oxide with ammonium bifluoride and H2SO4 to form a solution, separating off the Ta content by adding a soluble K compound to precipitate K fluorotantalate and then filtering to remove the precipitate; or (ii) converting impure Ta oxide to potassium (K) tantalate, combining the tantalate with NaF and H2SO4, separating the Ta content by adding a soluble K compound to precipitate (Na,K)2TaF7 and then filtering off the precipitate.