Adsorption of Ce(IV) Anionic Nitrato Complexes onto Anion Exchangers and Its Application for Ce(IV) Separation from Rare Earths(III)

Ce(IV) nitrato complexes were adsorbed on two anion exchangers based on polyvinyl pyridine (PVP) and quaternized PVP incorporated into porous silica matrix. The effect of nitric acid concentration (0.5∼6 mol·L−1) and temperature (278∼318 K) on Ce(IV) sorption efficiency was investigated. Sorption increased with increasing nitric acid concentration, indicating that [Ce(NO3)6]2− complex is the main adsorbed Ce(IV) species. Oxidation of sorbents by adsorbed Ce(IV) species resulting in Ce(III) release to the solution was observed. Pyridine based anion exchangers exhibited higher oxidation stability compared to the commercial strong base anion exchanger. Ce(IV) reduction was temperature dependent and obeyed pseudo-first-order reaction kinetics. Column separation of Ce(IV) from La(III) and Y(III) was carried out from 6 mol·L−1 nitric acid with PVP based anion exchanger. Reasonable Ce(IV) breakthrough capacity (0.7 mol·kg−1 PVP) was achieved. No remarkable decrease of capacity was observed within 3 consequent runs. In contrast, Ce(III) leakage due to reduction decreased and breakthrough capacity slightly increased. This effect was more pronounced with increasing temperature. Regeneration with 0.1 mol·L−1 nitric acid was successful (recovery 100%±4%) and Ce solution of high purity (>99.97%) with respect to La and Y content was gained.