Niobium and tantalum separation by gas-phase fluorination

The separation of tantalum and niobium compounds has been of interest for many years, with few new developments. Classically separation is achieved by liquid–liquid extraction and most research focuses on optimising this process. A separation method that bypasses the need for liquid–liquid extraction is reported here. The process uses dry fluorination to convert tantalum and niobium pentoxides into metal oxyfluorides. The thermal behaviour of these species is sufficiently different for separation to be achieved by preferential volatilisation. Experimental results indicate that at least two temperature ranges are suitable for separation, viz. one below 165 °C, and one above 650 °C.

Graphical abstractThermal separation of tantalum and niobium pentafluorides is not possible due to strong overlap of their sublimation temperatures. If the oxyfluorides are targeted, however, thermal separation is more feasible. Experimental results indicate that at least two temperature ranges are suitable for separation, viz. one below 165 °C, and one above 650 ºC.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Possibility to separate Nb/Ta oxide using a dry fluorination process is discussed. ► Volatilisation properties of specific model oxyfluorides are determined. ► Evidence is given on how an oxyfluoride sublimation system will work.