Separation of Group VB from Liquid Media
The Group VB elements of vanadium, niobium, and tantalum readily lose their outer shell electrons to form ions in solution. Vanadium forms two ions, V4+ and V5+, while a single ionic form is commonly found for the other two—Nb5+ and Ta5+. The Group VB elements are found as oxides, halides, sulfates, and mixed complexes. Due to their nearly identical atomic radii, Nb and Ta are virtually identical from a separation standpoint.
Vanadium, niobium, and tantalum are present as cations in acid, so a strong acid cation exchanger like AmberSep™ G26 H Resin is the separation media of choice. In dilute hydrochloric acid, V4+ has a high affinity for a strong acid cation resin. The affinity diminishes as the concentration increases from 4M to 8M HCl, but then the affinity increases again as acid concentration increases above 8M.
In perchloric acid, a strong acid cation resin has an even higher affinity for these cations.
In dilute nitric acid, V4+ has a high affinity for AmberSep™ G26 H and is eluted with higher concentrations of nitric acid.
In HF and HCl, these elements also form anions that can be captured on a strong base anion exchange resin like AmberSep™ 21K XLT Resin.1 A process for niobium and tantalum recovery has been described.2
Often these metals are being separated from other closely associated metals so resins with the maximum number of theoretical plates are needed. Strong acid cation fine mesh resins like AmberChrom™ 50WX8 100-200 Resin or AmberChrom™ 50WX4 100-200 Resin are proposed for this separation.
NOTICE: Oxidizing agents such as nitric acid attack organic ion exchange resins under certain conditions. This could lead to anything from slight resin degradation to a violent exothermic reaction (explosion). Before using strong oxidizing agents, consult sources knowledgeable in handling such materials.