Separation of Niobium and Tantalum Pentafluoride by Selective Precipitation Using p-Phenylenediamine

Abstract

The similarity between Ta and Nb chemistry makes it difficult to find the appropriate reagents and chemical reactions for the separation of the two elements. This study investigated the precipitation behavior of TaF^sub 5^ and NbF^sub 5^ with p-phenylenediamine (PPDA). PPDA preferentially precipitated Nb from a 1:1 ratio of NbF^sub 5^ and TaF^sub 5^. Niobium recoveries of >80%, and only 4% Ta, were found in the precipitate of the reaction between (Nb/Ta)F^sub 5^ and PPDA in ethanol. A separation factor of 100(9) indicated the potential for successful separation of Nb and Ta in a fluoride environment. A spectrophotometric study of the formation ratio of the newly formed Nb compound indicated a 1:1 metal:ligand ratio.