In alkaline carbonate solutions both technetium and uranium exist as anionic species, TcO 4 − and UO 2 (CO 3 ) 3 4− , which makes separating Tc and U from each other more challenging compared to acidic PUREX type solutions where uranium forms neutral or cationic complexes. We tested the batch separation of 99 Tc, 238 U, and 239 Pu from carbonate solutions using anion exchange resins with different properties, including Purolite A530E, Reillex HPQ, and Dowex Marathon WBA. Overall, the highest K d values for pertechnetate were achieved using the strong base resins in solutions of the lowest carbonate concentration. Pretreating the resins in higher carbonate concentrations before use was shown to increase the K d values for pertechnetate. The measured K d values for uranium generally were low, resulting in high selectivity for the separation of pertechnetate from uranium in carbonate solutions.
In the context of the demonstration of the UREX (uranium extraction) process, a separation of uranium and technetium using an anion exchange resin was performed on a simulant solution containing 98.95 g/L of 238U and 130.2 mg/L of 99Tc. After sorption on the resin, TcO4
− was eluted with NH4OH, the eluting stream was treated, and the technetium converted to Tc metal (yield=52.5%). The purity of the compound was analyzed: it contains less than 23.8 μg of 238U per gram of 99Tc. Tc metal was characterized by X-ray diffraction (XRD) and X-ray absorption fine structure (XAFS) spectroscopy; EXAFS analysis clearly confirms the hexagonal structure of the metal obtained after treatment. Uranium was converted to ammonium diuranate and to U3O8 in a yield of 88.2%, analysis indicates that the compound contains less than 0.16 μg of 99Tc per gram of ammonium diuaranate.
The behavior of neptunium in the ionic liquid betaine bistriflimide, [Hbet][Tf2N], has been studied spectroscopically at room temperature and 60 °C for the first time. An unprecedented complex redox chemistry is observed, with up to three oxidation states (iv, v and vi) and up to six Np species existing simultaneously. Both redox reactions and coordination of betaine are observed for Np(iv), (v) and (vi). Elevating the temperature accelerates the coordination of Np(v) with betaine and reduction reactions slow down.
A process to separate technetium from uranium in a simulated process solution resulting from the uranium extraction (UREX) process was demonstrated using a new extraction chromatographic (EC) resin from Eichrom Technologies. The Weak Base EC TM resin contains a tertiary amine incorporated into a macroporous resin bead support. The resin provided a good separation of pertechnetate from a 100 g/L uranyl(VI) nitrate solution representative of a UREX feed solution. The resin appeared quite stable to multiple uses. The elution of Tc from the resin was substantially improved over previous anion exchangers used. The eluted pertechnetate and ammonium nitrate solution was mixed with a reducing agent and gradually heated under an argon flow and then an argon/H 2 O flow to recover the Tc as the metal (96% yield). The U was precipitated with ammonium hydroxide and recovered as U 3 O 8 (98% yield).
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