Enhanced selective separation of vanadium(V) and chromium(VI) using the CeO 2 nanorod containing oxygen vacancies

Adsorption of vanadium from wastewater defends the environment from toxic ions and contributes to recover the valuable metal. However, it is still challenging for the separation of vanadium (V 5+ ) and chromium (Cr 6+ ) because of their similar properties. Herein, a kind of CeO 2 nanorod containing oxygen vacancies is facilely synthesized which displays ultra-high selectivity of V 5+ against various competitive ions (i.e., Fe, Mn, Cr, Ni, Cu, Zn, Ga, Cd, Ba, Pb, Mg, Be, and Co). Moreover, a large separation factor ( SF V/Cr ) of 114,169.14 for the selectivity of V 5+ is achieved at the Cr 6+ /V 5+ ratio of 80 with the trace amount of V 5+ (~ 1 mg/L). The results show that the process of V 5+ uptake is the monolayer homogeneous adsorption and is controlled by external and intraparticle diffusions. In addition, it also shows that V 5+ is reduced to V 3+ and V 4+ and then formation of V–O complexation. This work offers a novel CeO 2 nanorod material for efficient separation of V 5+ and Cr 6+ and also clarifies the mechanism of the V 5+ adsorption on the CeO 2 surface.