Vanadium, niobium, and tantalum are present as cations in acid, so a strong acid cation exchanger like DOWEX™ G 26 (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 DOWEX G-26 (H) and is eluted with higher concentrations of nitric acid.
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.
In HF and HCl, these elements also form anions that can be captured on a strong base anion exchange resin like DOWEX 21K XLT Resin1. A process for niobium and tantalum recovery has been described2.
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 DOWEX 50WX8 100 200 Resin or DOWEX 50WX4 100 200 Resin are proposed for this separation.
1 “Resin Selectivity in Dilute to Concentrated Aqueous Solutions" by R.M. Diamond and D.C. Whitney, Chapter 8 of Ion Exchange – A Series of Advances Edited by J.A. Marinshy, Published by Marcel Dekker, Inc., New York (1966).
2 "Ion exchange separation processes for Niobium and Tantalum." Barney, Duane L. and Kent, Clifford E., I&EC Process Design and Development 7 (1), 1-5 (1968).