Recovery of Tantalum using Dry Aqua Regia

Abstract

Tantalum (Ta), one of the rare metals, is mainly used for high-performance capacitors. While the increasing importance of Ta, its supply has many problems, e.g., imbalanced production and aspects such as conflict minerals. Recycling has a strong impact on the stable and responsible supply of materials, however, both hydro- and pyro-metallurgical procedures have many problems with the environmental impact and the operation cost. Considering the above situation, the authors have developed a novel recycling process of Ta using “dry aqua regia”. This is a molten salt consisting of ferric chloride (FeCl₃) and potassium chloride (KCl) and has already been applied for the recycling of platinum group metals (PGMs) and rare earth elements (REEs). In this study, the authors chlorinated Ta using this dry aqua regia and recovered tantalum oxide by the hydrolysis of chlorinated Ta. As a result, we succeeded in the chlorination of Ta at 630 - 670 K, which is a relatively low temperature for the pyrometallurgical procedure. Chlorinated Ta was recovered as an oxide by hydrolysis with water or nitric acid leaching, with impurities consisting of iron oxide. The recovery rate of Ta was up to 77.5 %, and the loss was suggested as volatilization during the chlorination. These results suggest that the procedure using “dry aqua regia” can be an effective recovery process for Ta.