Oxides
Metallurgy and recycling of niobium and tantalum

Oxide quality has risen sharply thanks to improvements in the hydrometallurgical process. At H.C. Starck, the metal impurity content of Ta₂O₅ fell from 1,350 to 22 ppm by mass between 1980 and 1990 [8].

These improvements have been achieved thanks to :

• a better understanding of the solvent extraction process;

• greater control over material flows, concentrations and acidity;

• the use of more corrosion-resistant materials in reactors.

The production of high-purity oxides for optical applications, such as the synthesis of crystals for optoelectrics, follows its own process: chlorination and successive distillation of the chlorides, followed by hydrolysis and calcination of the residue [19].