Selective separation of neptunium on macroporous bifunctional anion exchange resin aided by redox speciation

Abstract

Pyridinium and methyl ammonium based macroporous bifunctional anion exchange resin was synthesized from commercially available resin, Reillex™ 402 and investigated for selective extraction of neptunium(IV) from nitric acid medium. Acid stability of the resin was found to be satisfactory. Due to the possibility of existence as multiple oxidation states of Np, UV–Vis spectrophotometry and electrochemical methods were used to probe the redox speciation and warrant ion exchange separation of Np(IV). Ferrous sulphamate was used for simultaneous reduction of Np(V), (VI) and Pu(IV) to (IV) and (III), respectively. Batch sorption studies revealed fast kinetics (1 h.) of uptake having KD,NP(IV) of 425 at 4 M and capacity of 42 mg g−1. Stripping with ascorbic acid yielded quantitative results. Simultaneous determination of Np and Pu was standardized by electrochemical method. Selective separation of Np(IV) by column operation was carried out successfully for a mixture of (Np + Pu) and also (Np + Pu + U) corresponding to waste stream.