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The selective removal of the β‐emitting pertechnetate ion (99TcO4−) from nuclear waste streams is technically challenging. Herein, a practical approach is proposed for the selective removal of 99TcO4− (or its surrogate ReO4−) under extreme conditions of high acidity, alkalinity, ionic strength, and radiation field. Hollow porous N‐doped carbon capsules loaded with ruthenium clusters (Ru@HNCC) are first prepared, then modified with a cationic polymeric network (R) containing imidazolium‐N+ units (Ru@HNCC‐R) for selective 99TcO4− and ReO4− binding. The Ru@HNCC‐R capsules offer high binding affinities for 99TcO4−/ReO4− under wide‐ranging conditions. An electrochemical redox process then transforms adsorbed ReO4− to bulk ReO3, delivering record‐high removal capacities, fast kinetics, and excellent long‐term durability for removing ReO4− (as a proxy for 99TcO4−) in a 3 m HNO3, simulated nuclear waste‐Hanford melter recycle stream and an alkaline high‐level waste stream (HLW) at the U.S. Savannah River Site (SRS). In situ Raman and X‐ray absorption spectroscopy (XAS) analyses showed that adsorbed Re(VII) is electrocatalytically reduced on Ru sites to a Re(IV)O2 intermediate, which can then be re‐oxidized to insoluble Re(VI)O3 for facile collection. This approach overcomes many of the challenges associated with the selective separation and removal of 99TcO4−/ReO4− under extreme conditions, offering new vistas for nuclear waste management and environmental remediation. [ABSTRACT FROM AUTHOR]

Abstract The selective removal of the β‐emitting pertechnetate ion (99TcO4−) from nuclear waste streams is technically challenging. Herein, a practical approach is proposed for the selective removal of 99TcO4− (or its surrogate ReO4−) under extreme conditions of high acidity, alkalinity, ionic strength, and radiation field. Hollow porous N‐doped carbon capsules loaded with ruthenium clusters (Ru@HNCC) are first prepared, then modified with a cationic polymeric network (R) containing imidazolium‐N+ units (Ru@HNCC‐R) for selective 99TcO4− and ReO4− binding. The Ru@HNCC‐R capsules offer high binding affinities for 99TcO4−/ReO4− under wide‐ranging conditions. An electrochemical redox process then transforms adsorbed ReO4− to bulk ReO3, delivering record‐high removal capacities, fast kinetics, and excellent long‐term durability for removing ReO4− (as a proxy for 99TcO4−) in a 3 m HNO3, simulated nuclear waste‐Hanford melter recycle stream and an alkaline high‐level waste stream (HLW) at the U.S. Savannah River Site (SRS). In situ Raman and X‐ray absorption spectroscopy (XAS) analyses showed that adsorbed Re(VII) is electrocatalytically reduced on Ru sites to a Re(IV)O2 intermediate, which can then be re‐oxidized to insoluble Re(VI)O3 for facile collection. This approach overcomes many of the challenges associated with the selective separation and removal of 99TcO4−/ReO4− under extreme conditions, offering new vistas for nuclear waste management and environmental remediation.

Abstract Various types of polyoxometalates (POMs) have been synthesized since the 19th century, but their assortment has been mostly limited to Groups 5 and 6 metals. Herein, a new family of POMs composed of a carbon group element as the addenda atoms with two distinct phases, LnPbOClO4‐1 (Ln = Sm to Ho, Y) and LnPbOClO4‐2 (Ln = Er and Tm) is reported. Both structures are built from [Ln6O8] rare‐earth metal hexamers being incorporated in [Pb18O32]/[Pb12O24] polyplumbites, and unbound perchlorates as charge‐balancing anions. Impressively, YPbOClO4‐1 and ErPbOClO4‐2 exhibit exceptional uptake capacities (434.7 and 427.7 mg g−1) toward ReO4−, a chemical surrogate for the key radioactive fission product in the nuclear fuel cycle 99TcO4−, which are the highest values among all inorganic anion‐exchange materials reported until now. The sorption mechanism is clearly elucidated and visualized by single‐crystal‐to‐single‐crystal structural transformation from ErPbOClO4‐2 to a perrhenate‐containing complex ErPbOReO4, revealing a unique ReO4− uptake selectivity driven by specific interaction within Pb···O‐ReO3− bonds.

Various types of polyoxometalates (POMs) have been synthesized since the 19th century, but their assortment has been mostly limited to Groups 5 and 6 metals. Herein, a new family of POMs composed of a carbon group element as the addenda atoms with two distinct phases, LnPbOClO4‐1 (Ln = Sm to Ho, Y) and LnPbOClO4‐2 (Ln = Er and Tm) is reported. Both structures are built from [Ln6O8] rare‐earth metal hexamers being incorporated in [Pb18O32]/[Pb12O24] polyplumbites, and unbound perchlorates as charge‐balancing anions. Impressively, YPbOClO4‐1 and ErPbOClO4‐2 exhibit exceptional uptake capacities (434.7 and 427.7 mg g−1) toward ReO4−, a chemical surrogate for the key radioactive fission product in the nuclear fuel cycle 99TcO4−, which are the highest values among all inorganic anion‐exchange materials reported until now. The sorption mechanism is clearly elucidated and visualized by single‐crystal‐to‐single‐crystal structural transformation from ErPbOClO4‐2 to a perrhenate‐containing complex ErPbOReO4, revealing a unique ReO4− uptake selectivity driven by specific interaction within Pb···O‐ReO3− bonds. [ABSTRACT FROM AUTHOR]