Functional Carbon Capsules Supporting Ruthenium Nanoclusters for Efficient Electrocatalytic TcO /ReO Removal from Acidic and Alkaline Nuclear Wastes.

The selective removal of the β-emitting pertechnetate ion ( TcO ) from nuclear waste streams is technically challenging. Herein, a practical approach is proposed for the selective removal of TcO (or its surrogate ReO ) 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 TcO and ReO binding. The Ru@HNCC-R capsules offer high binding affinities for TcO /ReO under wide-ranging conditions. An electrochemical redox process then transforms adsorbed ReO to bulk ReO , delivering record-high removal capacities, fast kinetics, and excellent long-term durability for removing ReO (as a proxy for TcO ) in a 3 m HNO , 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)O intermediate, which can then be re-oxidized to insoluble Re(VI)O for facile collection. This approach overcomes many of the challenges associated with the selective separation and removal of TcO /ReO under extreme conditions, offering new vistas for nuclear waste management and environmental remediation.