Title : Separation of niobium and tantalum fluorides by precipitation with P-phenylenediamine
Abstract:
Both niobium and tantalum useful properties include high mechanical strength, high melting point, resistance to chemical attack, and low neutron absorption cross-section. These have resulted in a steady increase in demand for both metals over the last twenty years.1 Their importance in the production of modern industrial materials and high-tech consumer products ranges from super alloys in the production of jet engines, nuclear reactors, and space vehicle frames to hearing aids, laptop computers, mobile phones, video consoles, GPS, and digital cameras.2 The difficulty with working with these metals is getting them in their pure form appropriate for each application. This is partly because of their similar chemical properties and partly because of the difficulty in converting them into a form in which they can be easily separated.
As part of an ongoing study in the development of chemical processes for the separation and purification of Nb and Ta, it was decided to investigate precipitation methods for the separation of these metals from each other using pure NbF5, TaF5, Nb2O5, and Ta2O5 as starting materials. Powders of NbF5 and TaF5 were mixed in a 1 : 1 mole ratio and completely dissolved in 95 % absolute ethanol. The metal oxides (Nb2O5 and Ta2O5) were first converted fluorides by digestion with NH4HF2. Precipitation using p-phenylenediamine as a precipitant was found to be highly effective resulting in precipitation of greater than 80% Nb with only a maximum of 4% Ta.
Keywords: Tantalum fluoride, niobium fluoride, selective precipitation, quantitative analysis, recovery.
