Cation-exchange separation of uranium from thorium in nitric acid medium

Sorption behavior of Th and U on cation-exchange resins was investigated from nitric acid medium by both batch and column methods. The cation-exchange studies involved the sorption of UO22+ and Th4+ and their cationic complexes onto Dowex 50W x 8 and Dowex 50W x 4 resins (50-100 mesh). The batch data yielded a separation factor (Kd,Th/Kd,U) value of >100 for the cation-exchanger, Dowex 50W x 4 at 1-2M HNO3. Separation of uranium from thorium was also carried out by column method in nitric acid medium using cation-exchangers, Dowex 50Wx4 as well as Dowex 50Wx8. While uranium elution was possible at 1M HNO3, Th could be eluted only at higher concentration of nitric acid (>6M). The stripped solution emanating from a mixer settler employing di-2-ethyl hexyl isobutyramide as extractant and feed solution similar to THOREX process comprising 350 mg/l U and 380 mg/l Th in 0.75M HNO3 was loaded on the column and the decontamination factor value for U in the product was >1000. (author)